bpo-46576: Disable compiler optimization within test_peg_generator.

This speed up test_peg_generator by always disabling compiler optimizations by using -O0 by default when the test is building its own C extensions. A build not using --with-pydebug in order to speed up test execution winds up with this test taking a very long time as it would do repeated compilation of parser C code using the same optimization flags as CPython was built with. This speeds the test up 6-8x on gps-raspbian.
python · gpshead · Feb 2, 2022 · Jan 29, 2022 · Jan 30, 2022 · Jan 30, 2022
commit efbb64963df71ea0d54225e7dc2cb95eb44c4557
diff --git a/Misc/NEWS.d/next/Tests/2022-01-29-12-37-53.bpo-46576.-prRaV.rst b/Misc/NEWS.d/next/Tests/2022-01-29-12-37-53.bpo-46576.-prRaV.rst
@@ -0,0 +1,3 @@
+test_peg_generator now uses -O0 when testing compilation of its own C
+extensions to significantly speed up the compilation phase when testing
+non-debug builds of CPython.
@@ -32,6 +32,7 @@ def compile_c_extension(
     build_dir: Optional[str] = None,
     verbose: bool = False,
     keep_asserts: bool = True,
+    disable_optimization: bool = True,  # Significant test_peg_generator speedup.
 ) -> str:
     """Compile the generated source for a parser generator into an extension module.
 
@@ -61,6 +62,8 @@ def compile_c_extension(
     extra_link_args = get_extra_flags("LDFLAGS", "PY_LDFLAGS_NODIST")
     if keep_asserts:
         extra_compile_args.append("-UNDEBUG")
+    if disable_optimization:
+        extra_compile_args.append("-O0")
     extension = [
         Extension(
             extension_name,