Apply suggestions from code review

Co-authored-by: Victor Stinner <[email protected]>

Author: pablogsal

Lib/test/test_perf_profiler.py

@@ -24,14 +24,12 @@
 
 
 def is_jit_build():
-    cflags = sysconfig.get_config_var("PY_CORE_CFLAGS")
-    if not cflags:
-        return False
+    cflags = (sysconfig.get_config_var("PY_CORE_CFLAGS") or '')
     return "_Py_JIT" in cflags
 
 
 if is_jit_build():
-    raise unittest.SkipTest("Perf support is not available in jit builds")
+    raise unittest.SkipTest("Perf support is not available in JIT builds")
 
 
 def supports_trampoline_profiling():