[libcxx] [test] Merge the MinGW static/shared test config files (llvm#111759)

These were split in 0e8208e, with the
only functional difference between them at the time being `--prepend_env
PATH=%{lib-dir}` in the static config and `--prepend_env
PATH=%{install-prefix}/bin` in the shared library config.

However this difference is unnecessary - the static library config
doesn't need any `--prepend_env` argument at all. Before
0e8208e, both configurations used the
same config file, where the `--prepend_env` argument was unnecessary but
benign in the static case.

Reduce the unnecessary config duplication in this case, and return these
configs to using one single config file for both setups.

Author: mstorsjo

libcxx/CMakeLists.txt

@@ -131,11 +131,7 @@ option(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
 elseif(MINGW)
-  if (LIBCXX_ENABLE_SHARED)
-    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-mingw.cfg.in")
-  else()
-    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static-mingw.cfg.in")
-  endif()
+  set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-mingw.cfg.in")
 elseif(WIN32) # clang-cl
   if (LIBCXX_ENABLE_SHARED)
     set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-clangcl.cfg.in")

libcxx/test/configs/llvm-libc++-shared-mingw.cfg.in renamed to libcxx/test/configs/llvm-libc++-mingw.cfg.in

@@ -1,5 +1,5 @@
 # This testing configuration handles running the test suite against LLVM's libc++
-# using a DLL with MinGW/Clang on Windows.
+# using either a DLL or a static library, with MinGW/Clang on Windows.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')