Revert "[test] Default clang/test to FileCheck --allow-unused-prefixes=false"

This reverts commit 80f539526e.
Many test failures on mac: http://45.33.8.238/macm1/2772/summary.html
One on win: http://45.33.8.238/win/32442/summary.html

clang/test/Analysis/lit.local.cfg

@@ -26,3 +26,9 @@ config.substitutions.append(('%normalize_sarif',
 
 if not config.root.clang_staticanalyzer:
     config.unsupported = True
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# Insert this first. Then, we'll first update the blank FileCheck command; then,
+# the default substitution of FileCheck will replace it to its full path.
+config.substitutions.insert(0, (fc.regex,
+    'FileCheck --allow-unused-prefixes=false'))

clang/test/CodeGen/lit.local.cfg

@@ -0,0 +1,9 @@
+# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
+from lit.llvm.subst import ToolSubst
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# Insert this first. Then, we'll first update the blank FileCheck command; then,
+# the default substitution of FileCheck will replace it to its full path.
+config.substitutions.insert(0, (fc.regex,
+    'FileCheck --allow-unused-prefixes=false'))
+

clang/test/CodeGenCXX/lit.local.cfg

@@ -0,0 +1,9 @@
+# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
+from lit.llvm.subst import ToolSubst
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# Insert this first. Then, we'll first update the blank FileCheck command; then,
+# the default substitution of FileCheck will replace it to its full path.
+config.substitutions.insert(0, (fc.regex,
+    'FileCheck --allow-unused-prefixes=false'))
+

clang/test/Driver/lit.local.cfg

@@ -0,0 +1,26 @@
+from lit.llvm.subst import ToolSubst
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# Insert this first. Then, we'll first update the blank FileCheck command; then,
+# the default substitution of FileCheck will replace it to its full path.
+config.substitutions.insert(0, (fc.regex,
+    'FileCheck --allow-unused-prefixes=false'))
+
+config.suffixes = ['.c', '.cpp', '.h', '.m', '.mm', '.S', '.s', '.f90', '.F90', '.f95',
+                   '.cu', '.rs', '.cl', '.hip']
+config.substitutions = list(config.substitutions)
+config.substitutions.insert(0,
+    ('%clang_cc1',
+     """*** Do not use 'clang -cc1' in Driver tests. ***""") )
+
+# Remove harmful environmental variables for clang Driver tests.
+# Some might be useful for other tests so they are only removed here.
+driver_overwrite_env_vars = ['MACOSX_DEPLOYMENT_TARGET',
+                             'IPHONEOS_DEPLOYMENT_TARGET',
+                             'SDKROOT', 'CCC_OVERRIDE_OPTIONS',
+                             'CC_PRINT_OPTIONS', 'CC_PRINT_HEADERS',
+                             'CC_LOG_DIAGNOSTICS']
+
+for name in driver_overwrite_env_vars:
+  if name in config.environment:
+    del config.environment[name]

clang/test/OpenMP/lit.local.cfg

@@ -1,10 +0,0 @@
-# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
-from lit.llvm.subst import ToolSubst
-
-fc = ToolSubst('FileCheck', unresolved='fatal')
-# the parent introduced the opposite rule, so we replace it if we see it.
-if len(config.substitutions) > 0 and config.substitutions[0] == (fc.regex, 'FileCheck --allow-unused-prefixes=false'):
-    config.substitutions[0] = (
-        fc.regex, 'FileCheck --allow-unused-prefixes=true')
-else:
-    config.substitutions.insert(0, (fc.regex, 'FileCheck --allow-unused-prefixes=true'))

clang/test/lit.cfg.py

@@ -43,14 +43,6 @@ llvm_config.use_default_substitutions()
 
 llvm_config.use_clang()
 
-# FIXME: remove this when we flip the default value for --allow-unused-prefixes
-# to false.
-fc = ToolSubst('FileCheck', unresolved='fatal')
-# Insert this first. Then, we'll first update the blank FileCheck command; then,
-# the default substitution of FileCheck will replace it to its full path.
-config.substitutions.insert(0, (fc.regex,
-    'FileCheck --allow-unused-prefixes=false'))
-
 config.substitutions.append(
     ('%src_include_dir', config.clang_src_dir + '/include'))