Sync and add check for -nostdlib++ support.

Author: lntue

libc/cmake/modules/CheckCompilerFeatures.cmake

@@ -57,3 +57,5 @@ foreach(feature IN LISTS ALL_COMPILER_FEATURES)
 endforeach()
 
 message(STATUS "Compiler features available: ${AVAILABLE_COMPILER_FEATURES}")
+
+check_cxx_compiler_flag("-nostdlib++" LIBC_COMPILER_SUPPORT_NOSTDLIBPP)

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -435,6 +435,13 @@ function(add_libc_fuzzer target_name)
 
 endfunction(add_libc_fuzzer)
 
+# Get libgcc_s to be used in hermetic and integration tests.
+if(NOT LIBC_COMPILER_SUPPORT_NOSTDLIBPP)
+  execute_process(COMMAND ${CMAKE_CXX_COMPILER} -print-file-name=libgcc_s.so.1
+                  OUTPUT_VARIABLE LIBGCC_S_LOCATION)
+  string(STRIP ${LIBGCC_S_LOCATION} LIBGCC_S_LOCATION)
+endif()
+
 # DEPRECATED: Use add_hermetic_test instead.
 #
 # Rule to add an integration test. An integration test is like a unit test
@@ -564,10 +571,13 @@ function(add_integration_test test_name)
 
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
     target_link_options(${fq_build_target_name} PRIVATE -nostdlib -static)
-  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  elseif(LIBC_COMPILER_SUPPORT_NOSTDLIBPP)
     target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
   else()
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib -static)
+    # Older version of gcc does not support `nostdlib++` flag.  We use
+    # `nostdlib` and link against libgcc_s, which cannot be linked statically.
+    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib)
+    list(APPEND link_libraries ${LIBGCC_S_LOCATION})
   endif()
   target_link_libraries(
     ${fq_build_target_name}
@@ -743,10 +753,13 @@ function(add_libc_hermetic_test test_name)
 
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
     target_link_options(${fq_build_target_name} PRIVATE -nostdlib -static)
-  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  elseif(LIBC_COMPILER_SUPPORT_NOSTDLIBPP)
     target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
   else()
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib -static)
+    # Older version of gcc does not support `nostdlib++` flag.  We use
+    # `nostdlib` and link against libgcc_s, which cannot be linked statically.
+    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib)
+    list(APPEND link_libraries ${LIBGCC_S_LOCATION})
   endif()
   target_link_libraries(
     ${fq_build_target_name}