ci: set x86_64_v3_ARCH variable earlier

.github/workflows/mpv_clang.yml

@@ -51,6 +51,7 @@ jobs:
           elif [[ $BIT == "x86_64_v3" ]]; then
             echo "arch=x86_64" >> $GITHUB_ENV
             echo "x86_64_level=-v3" >> $GITHUB_ENV
+            echo "x86_64_v3_ARCH=-DGCC_ARCH=x86-64-v3" >> $GITHUB_ENV
           elif [[ $BIT == "aarch64" ]]; then
             echo "arch=aarch64" >> $GITHUB_ENV
           fi
@@ -101,7 +102,6 @@ jobs:
 
       - name: Configuring CMake & Downloading source
         run: |
-          if [[ $BIT == x86_64_v3 ]]; then echo "x86_64_v3_ARCH=-DGCC_ARCH=x86-64-v3" >> $GITHUB_ENV; fi
           cmake -DTARGET_ARCH=${{ env.arch }}-w64-mingw32 -DCOMPILER_TOOLCHAIN=clang ${{ env.x86_64_v3_ARCH }} -DCMAKE_INSTALL_PREFIX=$PWD/clang_root -DMINGW_INSTALL_PREFIX=$PWD/build_$BIT/$BIT-w64-mingw32 -DSINGLE_SOURCE_LOCATION=$PWD/src_packages -DRUSTUP_LOCATION=$PWD/clang_root/install_rustup -DENABLE_CCACHE=ON -DCLANG_PACKAGES_LTO=ON -G Ninja --fresh -B build_$BIT -S $PWD
           ninja -C build_$BIT download || true