[ci] Add checks that OpenMP is used in R-package builds (#4538)

.ci/test_r_package.sh

@@ -200,17 +200,23 @@ if grep -q -E "NOTE|WARNING|ERROR" "$LOG_FILE_NAME"; then
     exit -1
 fi
 
-# this check makes sure that CI builds of the CRAN package on Mac
-# actually use OpenMP
+# this check makes sure that CI builds of the package actually use OpenMP
 if [[ $OS_NAME == "macos" ]] && [[ $R_BUILD_TYPE == "cran" ]]; then
     omp_working=$(
         cat $BUILD_LOG_FILE \
         | grep --count -E "checking whether OpenMP will work .*yes"
     )
-    if [[ $omp_working -ne 1 ]]; then
-        echo "OpenMP was not found, and should be when testing the CRAN package on macOS"
-        exit -1
-    fi
+elif [[ $R_BUILD_TYPE == "cmake" ]]; then
+    omp_working=$(
+        cat $BUILD_LOG_FILE \
+        | grep --count -E ".*Found OpenMP: TRUE.*"
+    )
+else
+    omp_working=1
+fi
+if [[ $omp_working -ne 1 ]]; then
+    echo "OpenMP was not found"
+    exit -1
 fi
 
 # this check makes sure that CI builds of the CRAN package

.ci/test_r_package_windows.ps1

@@ -250,6 +250,15 @@ if ($env:R_BUILD_TYPE -eq "cran") {
   }
 }
 
+# Checking that OpenMP is actually used in CMake builds.
+if ($env:R_BUILD_TYPE -eq "cmake") {
+  $checks = Select-String -Path "${INSTALL_LOG_FILE_NAME}" -Pattern ".*Found OpenMP: TRUE.*"
+  if ($checks.Matches.length -eq 0) {
+    Write-Output "OpenMP wasn't found. Check the build logs."
+    Check-Output $False
+  }
+}
+
 if ($env:COMPILER -eq "MSVC") {
   Write-Output "Running tests with testthat.R"
   cd R-package/tests