Check*CompilerFlag: Avoid ';' in common pattern (#15048)

In commit v3.0.0-rc1~551^2~1 (Check*CompilerFlag: make C and CXX modules
share most error patterns, 2013-08-08) a pattern containing a ';' was
moved out of a ""-quoted argument and into a variable.  CMake flattens
the containing list and breaks the pattern.  Use a '.' to match ';'.

Modules/CMakeCheckCompilerFlagCommonPatterns.cmake

@@ -32,7 +32,7 @@ macro (CHECK_COMPILER_FLAG_COMMON_PATTERNS _VAR)
      FAIL_REGEX "[Ww]arning: [Oo]ption"                     # SunPro
      FAIL_REGEX "command option .* is not recognized"       # XL
      FAIL_REGEX "command option .* contains an incorrect subargument" # XL
-     FAIL_REGEX "not supported in this configuration; ignored"       # AIX
+     FAIL_REGEX "not supported in this configuration. ignored"       # AIX
      FAIL_REGEX "File with unknown suffix passed to linker" # PGI
      FAIL_REGEX "WARNING: unknown flag:"                    # Open64
      FAIL_REGEX "Incorrect command line option:"            # Borland