Make script work for any Swift version, and wasm SDK too

Author: jrflat

.github/workflows/pull_request.yml

@@ -10,11 +10,12 @@ jobs:
     uses: ./.github/workflows/swift_package_test.yml
     with:
       # Linux
-      linux_build_command: |
+      linux_pre_build_command: |
         mkdir MyPackage
         cd MyPackage
         swift package init --type library
-        swift build
+      linux_build_command: "swift build"
+      enable_linux_static_sdk_build: true
       # Windows
       windows_build_command: |
         mkdir MyPackage