macOS & GCC 9.2.0

As a follow-up to #20620 (closed), CMake 3.18.2 still does not build on macOS Catalina with GCC 9.2.0. In the LexerParser part, it raises the following error message:

[ 58%] Building CXX object Source/CMakeFiles/CMakeLib.dir/LexerParser/cmDependsJavaParser.cxx.o
[ 58%] Building CXX object Source/CMakeFiles/CMakeLib.dir/LexerParser/cmCommandArgumentParser.cxx.o
[ 58%] Building CXX object Source/CMakeFiles/CMakeLib.dir/LexerParser/cmFortranLexer.cxx.o
[ 58%] Building CXX object Source/CMakeFiles/CMakeLib.dir/LexerParser/cmExprParser.cxx.o
In file included from gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c
             ++/9.2.0/stdlib.h:36,
                 from Source/LexerParser/cmFortranLexer.cxx:232:
  >> 1902    gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c++/9.2.0/cstdlib:132:1
             1: error: '::aligned_alloc' has not been declared
  132 |   using ::aligned_alloc;
      |           ^~~~~~~~~~~~~
  >> 1905    make[2]: *** [Source/CMakeFiles/CMakeLib.dir/LexerParser/cmFortranLexer.cxx.o] Error 1
make[2]: *** Waiting for unfinished jobs....
In file included from gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c
             ++/9.2.0/stdlib.h:36,
                 from Source/LexerParser/cmExprLexer.cxx:232:
  >> 1909    gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c++/9.2.0/cstdlib:132:1
             1: error: '::aligned_alloc' has not been declared
  132 |   using ::aligned_alloc;
      |           ^~~~~~~~~~~~~
In file included from gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c
             ++/9.2.0/stdlib.h:36,
                 from Source/LexerParser/cmCommandArgumentLexer.cxx:232:
  >> 1914    gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c++/9.2.0/cstdlib:132:1
             1: error: '::aligned_alloc' has not been declared
  132 |   using ::aligned_alloc;
      |           ^~~~~~~~~~~~~
In file included from gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c
             ++/9.2.0/stdlib.h:36,
                 from Source/LexerParser/cmDependsJavaLexer.cxx:232:
  >> 1919    gcc-9.2.0-ie4mp5d7u3ygeu3icgelktq437acyzw6/include/c++/9.2.0/cstdlib:132:1
             1: error: '::aligned_alloc' has not been declared
  132 |   using ::aligned_alloc;
      |           ^~~~~~~~~~~~~
  >> 1922    make[2]: *** [Source/CMakeFiles/CMakeLib.dir/LexerParser/cmExprLexer.cxx.o] Error 1
  >> 1923    make[2]: *** [Source/CMakeFiles/CMakeLib.dir/LexerParser/cmCommandArgumentLexer.cxx.o] Error 1
  >> 1924    make[2]: *** [Source/CMakeFiles/CMakeLib.dir/LexerParser/cmDependsJavaLexer.cxx.o] Error 1
  >> 1925    make[1]: *** [Source/CMakeFiles/CMakeLib.dir/all] Error 2
  >> 1926    make: *** [all] Error 2

Related SO: https://stackoverflow.com/questions/52777209/compiler-cant-find-aligned-alloc-function/52777686#52777686

We see this in Spack for a GCC 9.2.0 that was built with AppleClang 11.0.0. We get the same problem with HomeBrew's gcc@9.3.0.