try support lower version macosx

Author: CppCXY

.github/workflows/build.yml

@@ -60,8 +60,8 @@ jobs:
         if: ${{ matrix.cross == 'general-macos-intel' }}
         run: |
           rustup target add ${{ matrix.target }}
-          export MACOSX_DEPLOYMENT_TARGET=10.15
-          cargo build --release --target ${{ matrix.target }} -p emmylua_ls
+          RUSTFLAGS="-C link-args=-mmacos-version-min=10.15" cargo build --release --target ${{ matrix.target }} -p emmylua_ls
+          otool -L target/${{ matrix.target }}/release/emmylua_ls | grep -A2 LC_BUILD_VERSION
       - name: copy-binary
         if: ${{ matrix.os != 'windows-latest'  }}
         run: |