Handle different installation layouts.

using  cmake option INSTALL_LAYOUT=STANDALONE would produce the layout as in 
tar.gz or zip packages.
INSTALL_LAYOUT=UNIX will produce unixish install layout  (with mysqld being in sbin subdirectory , libs in lib/mysql etc). This layout is used for RPM packages.

Subtle differences in both packages unfortunately lead to the need to recompile MySQL to use with other package type - as otherwise for example default plugins or data directories would be wrong set.

There are numerous other variables that  allow fine-tuning packaging layout. (INSTALL_BINDIR, INSTALL_LIBDIR , INSTALL_PLUGINDIR etc).

This options are different from autotools as they do not expect full paths to directories, but only subdirectory of CMAKE_INSTALL_PREFIX.

There are 2 special options that expect full directory paths
- MYSQL_DATADIR that defines default MYSQL data directory (autotools equivalent
is --localstatedir)
- SYSCONFDIR  can be added to search my.cnf search path (autotools equivalent is --sysconfdir)

scripts/mysqld_safe.sh

@@ -361,6 +361,9 @@ then
   if test -x "$MY_BASEDIR_VERSION/libexec/mysqld"
   then
     ledir="$MY_BASEDIR_VERSION/libexec"
+  elif test -x "$MY_BASEDIR_VERSION/sbin/mysqld"
+  then
+    ledir="$MY_BASEDIR_VERSION/sbin"
   else
     ledir="$MY_BASEDIR_VERSION/bin"
   fi
@@ -373,6 +376,10 @@ elif test -f "$relpkgdata"/english/errmsg.sys -a -x "$MY_PWD/libexec/mysqld"
 then
   MY_BASEDIR_VERSION="$MY_PWD"		# Where libexec, share and var are
   ledir="$MY_PWD/libexec"		# Where mysqld is
+elif test -f "$relpkgdata"/english/errmsg.sys -a -x "$MY_PWD/sbin/mysqld"
+then
+  MY_BASEDIR_VERSION="$MY_PWD"		# Where sbin, share and var are
+  ledir="$MY_PWD/sbin"			# Where mysqld is
 # Since we didn't find anything, used the compiled-in defaults
 else
   MY_BASEDIR_VERSION='@prefix@'