[CMake][Fuchsia] Use RelWithDebInfo to build runtimes

[phosek]

Summary

We want to preserve debug info in our runtimes to aid symbolization and
debugging; for shared libraries this will be stripped away during
install-stripped step and distributed via .build-id, for static archives
it's part of the archive and it's a responsibility of the consumer to
strip it away in the final binary if not needed.

[mcgrathr]

Lgtm

clang/cmake/caches/Fuchsia-stage2.cmake

if(APPLE)
   set(LIBCXX_ABI_VERSION 2 CACHE STRING "")
 endif()
 
 foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unknown-linux-gnu;x86_64-unknown-linux-gnu)
   if(LINUX_${target}_SYSROOT)
     # Set the per-target builtins options.
     list(APPEND BUILTIN_TARGETS "${target}")
     set(BUILTINS_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
-    set(BUILTINS_${target}_CMAKE_BUILD_TYPE Release CACHE STRING "")
+    set(BUILTINS_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_EXE_LINKER_FLAG "-fuse-ld=lld" CACHE STRING "")
 
     # Set the per-target runtimes options.
     list(APPEND RUNTIME_TARGETS "${target}")
     set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
-    set(RUNTIMES_${target}_CMAKE_BUILD_TYPE Release CACHE STRING "")
+    set(RUNTIMES_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_LLVM_ENABLE_ASSERTIONS ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_ENABLE_SHARED OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_INSTALL_LIBRARY OFF CACHE BOOL "")
foreach(target x86_64;aarch64)
     set(FUCHSIA_${target}_LINKER_FLAGS "-L${FUCHSIA_SDK}/arch/${FUCHSIA_${target}_NAME}/lib")
     set(FUCHSIA_${target}_SYSROOT "${FUCHSIA_SDK}/arch/${FUCHSIA_${target}_NAME}/sysroot")
   endforeach()
 
   foreach(target x86_64;aarch64)
     # Set the per-target builtins options.
     list(APPEND BUILTIN_TARGETS "${target}-unknown-fuchsia")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
-    set(BUILTINS_${target}-unknown-fuchsia_CMAKE_BUILD_TYPE Release CACHE STRING "")
+    set(BUILTINS_${target}-unknown-fuchsia_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_ASM_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_C_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_CXX_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_SHARED_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_MODULE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_EXE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}-unknown-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
 
     # Set the per-target runtimes options.
     list(APPEND RUNTIME_TARGETS "${target}-unknown-fuchsia")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
-    set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_BUILD_TYPE Release CACHE STRING "")
+    set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_BUILD_WITH_INSTALL_RPATH ON CACHE BOOL "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_ASM_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_C_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_CXX_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_SHARED_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_MODULE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_EXE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}-unknown-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")