Factor out common environment setup GHA steps

.github/workflows/ci.yml

@@ -258,24 +258,7 @@ jobs:
     - name: Configure
       run: |
           set -x
-
-          # Repeat language specific environment setup
-          case "$SWIGLANG" in
-            javascript)
-              case "$ENGINE" in
-                node)
-                  export NVM_DIR="$HOME/.nvm"
-                  [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"
-                  nvm use ${VER}
-                  ;;
-                *)
-              esac
-              ;;
-
-            ruby)
-              source $HOME/.rvm/scripts/rvm
-              ;;
-          esac
+          source Tools/CI-linux-environment.sh
 
           if test -n '${{ matrix.CONFIGOPTS }}'; then
             CONFIGOPTS=${{ matrix.CONFIGOPTS }}
@@ -298,24 +281,7 @@ jobs:
       working-directory: build/build
       run: |
           set -x
-
-          # Repeat language specific environment setup
-          case "$SWIGLANG" in
-            javascript)
-              case "$ENGINE" in
-                node)
-                  export NVM_DIR="$HOME/.nvm"
-                  [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"
-                  nvm use ${VER}
-                  ;;
-                *)
-              esac
-              ;;
-
-            ruby)
-              source $HOME/.rvm/scripts/rvm
-              ;;
-          esac
+          source Tools/CI-linux-environment.sh
 
           if test -n "$CPP11"; then export CPPSTD=c++11; fi
           if test -n "$CPP14"; then export CPPSTD=c++14; fi

Tools/CI-linux-environment.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+# Expected to be called from elsewhere with same variables set as CI-linux-install.sh
+# e.g. RETRY=travis-retry SWIGLANG=python
+# Sets up environment for using various target languages
+# For Github Actions where the environment is not preserved between steps
+set -e # exit on failure (same as -o errexit)
+
+case "$SWIGLANG" in
+	"javascript")
+		case "$ENGINE" in
+			"node")
+				export NVM_DIR="$HOME/.nvm"
+				[ -s "$NVM_DIR/nvm.sh" ] && source "$NVM_DIR/nvm.sh"
+				nvm use ${VER}
+				;;
+			*)      ;;
+		esac
+		;;
+	"ruby")
+		if ! command -v rvm; then
+			set +x
+			source $HOME/.rvm/scripts/rvm
+			set -x
+		fi
+		;;
+	*)	;;
+esac

Tools/CI-linux-install.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# expected to be called from elsewhere with certain variables set
+# Expected to be called from elsewhere with certain variables set
 # e.g. RETRY=travis-retry SWIGLANG=python GCC=7
 set -e # exit on failure (same as -o errexit)