[libc] disable integration tests when using gcc

The integration tests were failing to build under GCC due to missing
compile options for using LLVM's libc++ and compiler-rt.

This should unblock #60467

Reviewed By: sivachandra, lntue

Differential Revision: https://reviews.llvm.org/D145128

libc/test/CMakeLists.txt

@@ -25,8 +25,8 @@ if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
-if(NOT (${LIBC_TARGET_OS} STREQUAL "linux"))
-  # Integration tests are currently only available for linux.
+if(NOT (${LIBC_TARGET_OS} STREQUAL "linux") OR CMAKE_COMPILER_IS_GNUCXX)
+  # Integration tests are currently only available for clang on linux.
   return()
 endif()
 add_subdirectory(integration)

libc/test/src/CMakeLists.txt

@@ -60,12 +60,14 @@ if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(pthread)
 endif()
 
-if(LLVM_RUNTIMES_BUILD OR LIBC_HDRGEN_EXE)
+if(LLVM_RUNTIMES_BUILD OR LIBC_HDRGEN_EXE OR CMAKE_COMPILER_IS_GNUCXX)
   # The public API test below uses tablegen to generate the test
   # source file. Since tablegen is not available during a runtimes
   # build, we will skip the test.
   # If a different libc-hdrgen binary is being used, then also we
   # skip the api-test as we cannot generate the test source file.
+  # Additionally, this is an integration test and those only work with clang
+  # for the moment.
   return()
 endif()