[GA] try to force c++17

freebsd:
- go back to 13.2
- use c++17 instead of c++11
i386-linux:
- try to force c++17

git-svn-id: svn://tug.org/texlive/trunk/Build/source@72684 c570f23f-e606-0410-a88d-b1316a301751

.github/scripts/build-tl.sh

@@ -119,7 +119,10 @@ case "$arch" in
     export CC=gcc 
     export CXX=g++
     export CFLAGS=-D_NETBSD_SOURCE
-    export CXXFLAGS='-D_NETBSD_SOURCE -std=c++11'
+    export CXXFLAGS='-D_NETBSD_SOURCE -std=c++17'
+    ;;
+  i386-linux)
+    export CXXFLAGS='-std=c++17'
     ;;
 esac
 export TL_MAKE_FLAGS

.github/workflows/main.yml

@@ -148,7 +148,7 @@ jobs:
         uses: vmactions/freebsd-vm@v1
         if: ${{ matrix.os == 'freebsd' && (matrix.ci_build || matrix.release_build) }}
         with: 
-          release: '14.1'
+          release: '13.2'
           usesh: true
           run: |
             cd repo