Fix package build failure when the compiler types not defined (Fixes #20428) (#20429)

This fixes the install issue #20428
by adding a default value when a compiler type is not defined. While
this fix is specifically for z/OS, it should also fix other platforms
that have their compiler_type changed in distutils/setuptools such as
mingw32.

I tested this with installing the librt package. I've added no testcases
as there's no new functionality.

Author: pitmanst

mypyc/build_setup.py

@@ -48,7 +48,7 @@ def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
                 new_cmd.extend(["-msimd128"])
     else:
         compiler_type: str = self.compiler_type
-        extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT[compiler_type]
+        extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT.get(compiler_type, None)
         new_cmd = list(cmd)
         if X86_64 and extra_options is not None:
             # filenames are closer to the end of command line

mypyc/lib-rt/build_setup.py

@@ -48,7 +48,7 @@ def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
                 new_cmd.extend(["-msimd128"])
     else:
         compiler_type: str = self.compiler_type
-        extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT[compiler_type]
+        extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT.get(compiler_type, None)
         new_cmd = list(cmd)
         if X86_64 and extra_options is not None:
             # filenames are closer to the end of command line