cmake: Fix #4038 MacOS target older OS and SDK versions

This fix ensures that when `MACOSX_DEPLOYMENT_TARGET` and `SDKROOT` are set, they are respected when building the libraries and executables.

diff --git a/Makefile b/Makefile
index 95d45afb46dd4e35a308f64cfb1570332c7ae5ea..e80505b7f369b4ee50ca30a6c3c57342df92b712 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -200,9 +200,9 @@ travis-install:
 .PHONY: clangbuild-darwin-fat
 clangbuild-darwin-fat: clean
        clang -v
-       CXX=clang++ CC=clang CFLAGS="-Werror -Wconversion -Wno-sign-conversion -Wdocumentation -arch arm64" $(MAKE) zstd-release
+       CXX=clang++ CC=clang CFLAGS+="-Werror -Wconversion -Wno-sign-conversion -Wdocumentation -arch arm64" $(MAKE) zstd-release
        mv programs/zstd programs/zstd_arm64
-       CXX=clang++ CC=clang CFLAGS="-Werror -Wconversion -Wno-sign-conversion -Wdocumentation -arch x86_64" $(MAKE) zstd-release
+       CXX=clang++ CC=clang CFLAGS+="-Werror -Wconversion -Wno-sign-conversion -Wdocumentation -arch x86_64" $(MAKE) zstd-release
        mv programs/zstd programs/zstd_x64
        lipo -create programs/zstd_x64 programs/zstd_arm64 -output programs/zstd