flang: check CI instead of GITHUB_ACTIONS env var.

autobuild filters out all env vars starting with GITHUB_ or RUNNER_, so
this check failed there.

What I really want to detect is whether it is running on a Github-hosted
runner, but I don't know a good way to do so.

mingw-w64-flang/PKGBUILD

@@ -3,7 +3,7 @@ _realname=flang
 pkgbase=mingw-w64-${_realname}
 pkgname=("${MINGW_PACKAGE_PREFIX}-${_realname}")
 pkgver=13.0.0
-pkgrel=1
+pkgrel=2
 pkgdesc="Fortran frontend for LLVM (mingw-w64)"
 arch=('any')
 mingw_arch=('mingw32' 'mingw64' 'ucrt64' 'clang64' 'clang32' 'clangarm64')
@@ -82,7 +82,7 @@ build() {
     # figure about 1 job per 2GB RAM
     local _jobs=$(awk '{ if ($1 == "MemTotal:") { printf "%.0f", $2/(2*1024*1024) } }' /proc/meminfo)
     # EXCEPT on GHA, which is being really difficult.
-    if (( _jobs < 1 )) || [ -n "${GITHUB_ACTIONS+x}" ]; then
+    if (( _jobs < 1 )) || [ -n "${CI+x}" ]; then
       _jobs=1
     elif (( _jobs > $(nproc) + 2 )); then
       _jobs=$(( $(nproc) + 2 ))