cmake: Report if the <LANG>_CLANG_TIDY tool exits with non-zero

When using `<LANG>_CLANG_TIDY` our internal launcher for the tool must
capture its return code and stderr and report them on failure.
Otherwise incorrect command lines silently fail.

Closes: #16435

1 files changed, 6 insertions, 0 deletions

diff --git a/Tests/RunCMake/pseudo_tidy.c b/Tests/RunCMake/pseudo_tidy.c
index c950d03..2feeb0f 100644
--- a/Tests/RunCMake/pseudo_tidy.c
+++ b/Tests/RunCMake/pseudo_tidy.c
@@ -1,9 +1,15 @@
 #include <stdio.h>
+#include <string.h>
 
 int main(int argc, char* argv[])
 {
   int i;
   for (i = 1; i < argc; ++i) {
+    if (strcmp(argv[i], "-bad") == 0) {
+      fprintf(stdout, "stdout from bad command line arg '-bad'\n");
+      fprintf(stderr, "stderr from bad command line arg '-bad'\n");
+      return 1;
+    }
     if (argv[i][0] != '-') {
       fprintf(stdout, "%s:0:0: warning: message [checker]\n", argv[i]);
       break;