CI - clang-format-18 (#9225)

* Fix shell variable comparison without $CI present

+ '[' = true ']'
./tests/restyle.sh: line 16: [: =: unary operator expected

vs.

+ '[' '' = true ']'

* Update to clang-format-18

new opt to skip overly eager macro formatting
https://clang.llvm.org/docs/ClangFormatStyleOptions.html#skipmacrodefinitionbody

minor changes between 15 and 18 for ide examples

reference arduino-ide format is still stuck with 15, though
https://github.com/arduino/clang-static-binaries/releases

* Pin clang-format in CI recipe not the script itself

* style

tests/device/libraries/BSTest/src/BSTest.h

@@ -27,8 +27,7 @@ class TestCase
 public:
     TestCase(TestCase* prev, test_case_func_t func, const char* file, size_t line, const char* name,
              const char* desc) :
-        m_func(func),
-        m_file(file), m_line(line), m_name(name), m_desc(desc)
+        m_func(func), m_file(file), m_line(line), m_name(name), m_desc(desc)
     {
         if (prev)
         {