meson CI: use env section

Avoids having to use env.exe

Signed-off-by: Rosen Penev <rosenp@gmail.com>

.github/workflows/on_PR_meson.yaml

@@ -24,8 +24,10 @@ jobs:
           python3 -m pip install meson ninja
 
       - name: Sanity Checks
+        env:
+          CXX: g++-${{matrix.cxx}}
         run: |
-          env CXX=g++-${{matrix.cxx}} meson setup "${{github.workspace}}/build" --wrap-mode=${{matrix.deps}} -Ddefault_library=${{matrix.type}} -Dwarning_level=3
+          meson setup "${{github.workspace}}/build" --wrap-mode=${{matrix.deps}} -Ddefault_library=${{matrix.type}} -Dwarning_level=3
           meson compile -C "${{github.workspace}}/build" --verbose
           meson test -C "${{github.workspace}}/build" --verbose
 

.github/workflows/on_PR_meson_clang.yaml

@@ -24,7 +24,10 @@ jobs:
           python3 -m pip install meson ninja
 
       - name: Sanity Checks
+        env:
+          CXX: clang++-${{matrix.cxx}}
+          CXXFLAGS: -stdlib=libc++
         run: |
-          env CXX=clang++-${{matrix.cxx}} CXXFLAGS=-stdlib=libc++ meson setup "${{github.workspace}}/build" --wrap-mode=${{matrix.deps}} -Ddefault_library=${{matrix.type}} -Dwarning_level=3 -Dcpp_std=c++20
+          meson setup "${{github.workspace}}/build" --wrap-mode=${{matrix.deps}} -Ddefault_library=${{matrix.type}} -Dwarning_level=3 -Dcpp_std=c++20
           meson compile -C "${{github.workspace}}/build" --verbose
           meson test -C "${{github.workspace}}/build" --verbose