Rewrite test common/100 manygen using get_argument_syntax(), so it
treats clang-cl as cl, can handle only clang-cl being available, and try
to make it a bit less convoluted.
The code generated manually with manygen.py must use the same CRT
compiler arguments as the final executable itself or we get an error
during linking:
MSVCRTD.lib(_chandler4gs_.obj) : error LNK2019: unresolved external symbol __except_handler4_common referenced in function __except_handler4
depuser.exe : fatal error LNK1120: 1 unresolved externals