[clang][scan-build] Trust users' compiler choice

If you went out of your way to specify the option, you probably knew
what you wanted and didn't want the default you'd get from not
specifying the option in the first place.

We just let the error from from system() propagate to tell the user that
the option they provided wasn't usable:

  $ scan-build-19 --use-cc="enoent gcc" make
  scan-build: Using '/usr/lib/llvm-19/bin/clang' for static analysis
  ...
  Can't exec "enoent": No such file or directory ...

Author: rafl

clang/tools/scan-build/libexec/ccc-analyzer

@@ -51,17 +51,6 @@ sub silent_system {
 # Compiler command setup.
 ##===----------------------------------------------------------------------===##
 
-# Search in the PATH if the compiler exists
-sub SearchInPath {
-    my $file = shift;
-    foreach my $dir (split (':', $ENV{PATH})) {
-        if (-x "$dir/$file") {
-            return 1;
-        }
-    }
-    return 0;
-}
-
 {
   my ($DefaultCCompiler, $DefaultCXXCompiler);
 
@@ -81,13 +70,7 @@ sub SearchInPath {
     my ($is_cxx) = @_;
     my $default = $is_cxx ? $DefaultCXXCompiler : $DefaultCCompiler;
     my $opt = $ENV{$is_cxx ? 'CCC_CXX' : 'CCC_CC'};
-    return $default unless defined $opt;
-    my ($comp, @args) = shellwords($opt);
-    if (!-x $comp && !SearchInPath($comp)) {
-      warn "Can't execute '$comp'. Falling back to '$default'.\n";
-      return $default;
-    }
-    return ($comp, @args);
+    return defined $opt ? shellwords($opt) : $default;
   }
 }