Decrement MACOSX_DEPLOYMENT_TARGET to fix CI build

Author: Noremos

vcpkg-custom/registry/ports/libcxx/19.1.1_0/build.sh.in

@@ -5,7 +5,7 @@ set -e
 SOURCE_PATH=@SOURCE_PATH@
 INSTALL_PREFIX=@INSTALL_PREFIX@
 
-export MACOSX_DEPLOYMENT_TARGET=14.6
+export MACOSX_DEPLOYMENT_TARGET=12.7
 
 cmake -G Ninja -S $SOURCE_PATH/llvm \
 	-DCMAKE_INSTALL_PREFIX=$INSTALL_PREFIX \