Ensure that grep -P works

The `--perl-regexp` option of `grep` requires a "unibyte or UTF-8"
locale, simply refusing to work at all if neither `LANG`, `LC_ALL` nor
`LC_CTYPE` are set.

Typically, this would not be a problem because `/etc/profile` ensures
that `LC_CTYPE` is set. But GitHub workflows call `bash` with
`-noprofile`, therefore we need to do set `LC_CTYPE` here. Just like
`/etc/profile` does, we won't override any locale the user might have
configured explicitly.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/test.yml

@@ -51,3 +51,6 @@ jobs:
           gcc -o hello-world.exe hello-world.c
           hello="$(./hello-world.exe)"
           test 'Hello, world!' = "$hello"
+
+          # Verify that the locale is set, enabling `grep -P` to work
+          test 123 = "$(printf '1248\n123\n' | grep -P '2(?!4)')"

.vscode/settings.json

@@ -1,6 +1,7 @@
 {
     "cSpell.ignoreRegExpList": [
         "CHERE_INVOKING",
+        "LC_CTYPE",
         "SDK's",
         "makepkg-git",
         "mingw-w64-git",

main.ts

@@ -62,6 +62,13 @@ async function run(): Promise<void> {
     const msystem = architecture === 'i686' ? 'MINGW32' : 'MINGW64'
     core.addPath(`${outputDirectory}/${msystem.toLocaleLowerCase()}/bin`)
     core.exportVariable('MSYSTEM', msystem)
+    if (
+      !('LANG' in process.env) &&
+      !('LC_ALL' in process.env) &&
+      !('LC_CTYPE' in process.env)
+    ) {
+      core.exportVariable('LC_CTYPE', 'C.UTF-8')
+    }
   } catch (error) {
     core.setFailed(error.message)
   }