Fix cmake_build_type typo

Author: Changqing-JING

Makefile

@@ -178,7 +178,7 @@ LIBCXX_CMAKE_FLAGS = \
     -DLIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY:BOOL=OFF \
     -DLIBCXX_HAS_WIN32_THREAD_API:BOOL=OFF \
     -DLLVM_COMPILER_CHECKED=ON \
-    -DCMAKE_BUILD_TYPE=RelWithDebugInfo \
+    -DCMAKE_BUILD_TYPE=RelWithDebInfo \
     -DLIBCXX_ENABLE_SHARED:BOOL=$(2) \
     -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL=OFF \
     -DLIBCXX_ENABLE_EXCEPTIONS:BOOL=OFF \