[debuginfo-tests][dexter] Add --builder gcc support for POSIX

[Pierre-vh]

Summary

During our tests, we found that Dexter lacked GCC support, so we added --builder GCC support and we now propose to upstream it.
We think that having GCC support in Dexter is a great idea as it allows us to make comparisons between Clang and GCC.

This is a rather trivial change:

• Added a gcc.sh script (for POSIX systems) that invokes GCC instead of clang. The script is very similar to the clang.sh script in the same folder.
• Added an implementation of _verify_options in the clang_opt_bisect tool so it'll refuse to run when the builder is GCC

[jmorse]

Would it not be possible to override handle_options in the tool class, put the logic from _verify_options there (raising an Error if there's a problem), and then call super(Tool,self).handle_options() if there's no error? This would avoid the need to add a new method / code path.

Otherwise, adding a gcc builder sounds great!

[Pierre-vh]

In D75339#1901101, @jmorse wrote:

Would it not be possible to override handle_options in the tool class, put the logic from _verify_options there (raising an Error if there's a problem), and then call super(Tool,self).handle_options() if there's no error? This would avoid the need to add a new method / code path.

Otherwise, adding a gcc builder sounds great!

This is definitely possible, but I did it that way because my other change (the gen tool RFC) also needs a similar feature (see the parent diff: D75337)
If you prefer, I can change both this diff and D75343 to do what you suggested, then I can simply delete the parent revision (D75337).

[Pierre-vh]

Here is the updated revision with _verify_options removed.
Note that it also contains 2 minor formatting fixes, but if you want I can remove them.

[jmorse]

LGTM

debuginfo-tests/dexter/dex/builder/scripts/posix/gcc.sh

+#!/usr/bin/env bash
+set -e
+
+if test -z "$PATHTOGCC"; then
+  PATHTOGCC=gcc
+fi
+
+for INDEX in $SOURCE_INDEXES
+do
+  CFLAGS=$(eval echo "\$COMPILER_OPTIONS_$INDEX")
+  SRCFILE=$(eval echo "\$SOURCE_FILE_$INDEX")
+  OBJFILE=$(eval echo "\$OBJECT_FILE_$INDEX")
+  $PATHTOGCC -std=gnu++11 -c $CFLAGS $SRCFILE -o $OBJFILE
+done
+
+$PATHTOGCC $LINKER_OPTIONS $OBJECT_FILES -o $EXECUTABLE_FILE

debuginfo-tests/dexter/dex/tools/clang_opt_bisect/Tool.py

def _get_bisect_limits(self):
             options.source_files), (results, options.source_files)
 
         limits = [
             int(Tool._re_running_pass.match(r).group(1)) for r in results
         ]
 
         return limits
 
+    def _verify_options(self, options) -> bool:
+        if "clang" not in options.builder.lower():
+            self.context.o.auto("error: --builder %s is not supported by the clang-opt-bisect tool - only 'clang' is "
+                                "supported\n " % options.builder)
+            return False
+        return True
+
     def _run_test(self, test_name):  # noqa
         options = self.context.options
 
         per_pass_score = []
         current_bisect_pass_summary = defaultdict(list)
 
         max_limits = self._get_bisect_limits()
         overall_limit = sum(max_limits)