[runtimes] Rename the %{flags} Lit substitution to %{common_flags}

[ldionne]

These flags are common to compilation and linking, so %{common_flags} makes more sense.

[github-actions]

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darker --check --diff -r origin/main...HEAD libcxx/test/benchmarks/spec.gen.py libcxx/test/libcxx-03/module_std.gen.py libcxx/test/libcxx-03/module_std_compat.gen.py libcxx/test/libcxx/module_std.gen.py libcxx/test/libcxx/module_std_compat.gen.py libcxx/utils/libcxx/test/config.py libcxx/utils/libcxx/test/dsl.py libcxx/utils/libcxx/test/format.py

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View the diff from darker here.

--- test/benchmarks/spec.gen.py	2025-12-19 00:19:33.000000 +0000
+++ test/benchmarks/spec.gen.py	2025-12-19 00:21:03.445044 +0000
@@ -20,20 +20,21 @@
 import json
 import pathlib
 import sys
 
 test_dir = pathlib.Path(sys.argv[1])
-cxx = (test_dir / 'cxx.subs').open().read().strip()
-compile_flags = (test_dir / 'compile_flags.subs').open().read().strip()
-common_flags = (test_dir / 'common_flags.subs').open().read().strip()
-link_flags = (test_dir / 'link_flags.subs').open().read().strip()
-spec_dir = pathlib.Path((test_dir / 'spec_dir.subs').open().read().strip())
+cxx = (test_dir / "cxx.subs").open().read().strip()
+compile_flags = (test_dir / "compile_flags.subs").open().read().strip()
+common_flags = (test_dir / "common_flags.subs").open().read().strip()
+link_flags = (test_dir / "link_flags.subs").open().read().strip()
+spec_dir = pathlib.Path((test_dir / "spec_dir.subs").open().read().strip())
 
 # Setup the configuration file
 test_dir.mkdir(parents=True, exist_ok=True)
-spec_config = test_dir / 'spec-config.cfg'
-spec_config.write_text(f"""
+spec_config = test_dir / "spec-config.cfg"
+spec_config.write_text(
+    f"""
 default:
     ignore_errors        = 1
     iterations           = 1
     label                = spec-stdlib
     log_line_width       = 4096
@@ -48,11 +49,12 @@
     CC                   = cc -O3 -std=c18 -Wno-implicit-function-declaration
     CXX                  = {cxx} {compile_flags} {common_flags} {link_flags} -Wno-error
     CC_VERSION_OPTION    = --version
     CXX_VERSION_OPTION   = --version
     EXTRA_PORTABILITY    = -DSPEC_NO_CXX17_SPECIAL_MATH_FUNCTIONS # because libc++ doesn't implement the special math functions yet
-""")
+"""
+)
 
 # Build the list of benchmarks. We take all intrate and fprate benchmarks that contain C++ and
 # discard the ones that contain Fortran, since this test suite isn't set up to build Fortran code.
 spec_benchmarks = set()
 no_fortran = set()
--- utils/libcxx/test/config.py	2025-12-19 00:19:33.000000 +0000
+++ utils/libcxx/test/config.py	2025-12-19 00:21:03.506917 +0000
@@ -49,10 +49,17 @@
                     action.pretty(config, lit_config.params), feature.pretty(config)
                 )
             )
 
     # Print the basic substitutions
-    for sub in ("%{cxx}", "%{common_flags}", "%{compile_flags}", "%{link_flags}", "%{benchmark_flags}", "%{exec}"):
+    for sub in (
+        "%{cxx}",
+        "%{common_flags}",
+        "%{compile_flags}",
+        "%{link_flags}",
+        "%{benchmark_flags}",
+        "%{exec}",
+    ):
         note("Using {} substitution: '{}'".format(sub, _getSubstitution(sub, config)))
 
     # Print all available features
     note("All available features: {}".format(", ".join(sorted(config.available_features))))
--- utils/libcxx/test/format.py	2025-12-19 00:19:33.000000 +0000
+++ utils/libcxx/test/format.py	2025-12-19 00:21:03.803778 +0000
@@ -29,11 +29,18 @@
     return tmpDir, tmpBase
 
 
 def _checkBaseSubstitutions(substitutions):
     substitutions = [s for (s, _) in substitutions]
-    for s in ["%{cxx}", "%{compile_flags}", "%{link_flags}", "%{benchmark_flags}", "%{common_flags}", "%{exec}"]:
+    for s in [
+        "%{cxx}",
+        "%{compile_flags}",
+        "%{link_flags}",
+        "%{benchmark_flags}",
+        "%{common_flags}",
+        "%{exec}",
+    ]:
         assert s in substitutions, "Required substitution {} was not provided".format(s)
 
 def _executeScriptInternal(test, litConfig, commands):
     """
     Returns (stdout, stderr, exitCode, timeoutInfo, parsedCommands), or an appropriate lit.Test.Result
@@ -92,11 +99,14 @@
     #       errors, which doesn't make sense for clang-verify tests because we may want to check
     #       for specific warning diagnostics.
     _checkBaseSubstitutions(substitutions)
     substitutions.append(("%{temp}", tmpDir))
     substitutions.append(
-        ("%{build}", "%{cxx} %s %{common_flags} %{compile_flags} %{link_flags} -o %t.exe")
+        (
+            "%{build}",
+            "%{cxx} %s %{common_flags} %{compile_flags} %{link_flags} -o %t.exe",
+        )
     )
     substitutions.append(
         (
             "%{verify}",
             "%{cxx} %s %{common_flags} %{compile_flags} -U_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -fsyntax-only -Wno-error -Xclang -verify -Xclang -verify-ignore-unexpected=note -ferror-limit=0",