../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-exit.o):(.literal+0x4): undefined reference to `_exit'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-exit.o): In function `exit':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/exit.c:65: undefined reference to `_exit'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-fopen.o):(.literal+0x0): undefined reference to `_open_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-fopen.o): In function `_fopen_r':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/fopen.c:141: undefined reference to `_open_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-freer.o):(.literal+0x14): undefined reference to `_sbrk_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-freer.o): In function `_malloc_trim_r':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/mallocr.c:3325: undefined reference to `_sbrk_r'
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/mallocr.c:3332: undefined reference to `_sbrk_r'
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/mallocr.c:3340: undefined reference to `_sbrk_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-fseeko.o):(.literal+0x10): undefined reference to `_fstat_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-fseeko.o): In function `_fseeko_r':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/fseeko.c:231: undefined reference to `_fstat_r'
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/fseeko.c:258: undefined reference to `_fstat_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-makebuf.o): In function `__smakebuf_r':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/makebuf.c:59: undefined reference to `_fstat_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-mallocr.o): In function `malloc_extend_top':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/mallocr.c:2165: undefined reference to `_sbrk_r'
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdlib/../../../../../newlib/libc/stdlib/mallocr.c:2202: undefined reference to `_sbrk_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o):(.literal+0x4): undefined reference to `_read_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o):(.literal+0x8): undefined reference to `_lseek_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o):(.literal+0xc): undefined reference to `_write_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o):(.literal+0x10): undefined reference to `_close_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o): In function `__sread':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/stdio.c:48: undefined reference to `_read_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o): In function `__swrite':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/stdio.c:89: undefined reference to `_lseek_r'
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/stdio.c:97: undefined reference to `_write_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o): In function `__sseek':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/stdio.c:117: undefined reference to `_lseek_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-stdio.o): In function `__sclose':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\stdio/../../../../../newlib/libc/stdio/stdio.c:135: undefined reference to `_close_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-sysclose.o): In function `close':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\syscalls/../../../../../newlib/libc/syscalls/sysclose.c:10: undefined reference to `_close_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-time.o):(.literal+0x0): undefined reference to `_gettimeofday_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(lib_a-time.o): In function `time':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\time/../../../../../newlib/libc/time/time.c:46: undefined reference to `_gettimeofday_r'
../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/lib\libc.a(isatty.o): In function `_isatty_r':
d:\Neo\Project\ESP8266\DevKit\build\compiler\dl\esp-newlib\build\xtensa-lx106-elf\newlib\libc\sys\xtensa/../../../../../../newlib/libc/sys/xtensa/isatty.c:13: undefined reference to `_fstat_r'
collect2.exe: error: ld returned 1 exit status
Quoting the serial.port will enable esptool to work for dev/tty devices with spaces in their name. Like in OSX: `/dev/tty.wch ch341 USB=>RS232 fa130`. Without quote the esptool fails silently since it only parses the `/dev/tty.wch`.