depends: fix osx build with clang 16

For some reason the previous syntax worked with clang 15 and below, but
clang 16 requires that the option and value are properly separated.

depends/hosts/darwin.mk

@@ -99,8 +99,8 @@ darwin_CC=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
             $(clang_prog) --target=$(host) -mmacosx-version-min=$(OSX_MIN_VERSION) \
               -B$(build_prefix)/bin -mlinker-version=$(LD64_VERSION) \
               -isysroot$(OSX_SDK) \
-              -Xclang -internal-externc-isystem$(clang_resource_dir)/include \
-              -Xclang -internal-externc-isystem$(OSX_SDK)/usr/include
+              -Xclang -internal-externc-isystem -Xclang $(clang_resource_dir)/include \
+              -Xclang -internal-externc-isystem -Xclang $(OSX_SDK)/usr/include
 darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
                -u OBJC_INCLUDE_PATH -u OBJCPLUS_INCLUDE_PATH -u CPATH \
                -u LIBRARY_PATH \
@@ -109,8 +109,8 @@ darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
                -isysroot$(OSX_SDK) \
                -stdlib=libc++ \
                -stdlib++-isystem$(OSX_SDK)/usr/include/c++/v1 \
-               -Xclang -internal-externc-isystem$(clang_resource_dir)/include \
-               -Xclang -internal-externc-isystem$(OSX_SDK)/usr/include
+               -Xclang -internal-externc-isystem -Xclang $(clang_resource_dir)/include \
+               -Xclang -internal-externc-isystem -Xclang $(OSX_SDK)/usr/include
 
 darwin_CFLAGS=-pipe -std=$(C_STANDARD)
 darwin_CXXFLAGS=-pipe -std=$(CXX_STANDARD)