[flang][driver] Introduce FCC_OVERRIDE_OPTIONS. (#140556)

This PR add functionality to change `flang` command line using
environment variable `FCC_OVERRIDE_OPTIONS`. It is quite similar to what
`CCC_OVERRIDE_OPTIONS` does for clang.

The `FCC_OVERRIDE_OPTIONS` seemed like the most obvious name to me but I
am open to other ideas. The `applyOverrideOptions` now takes an extra
argument that is the name of the environment variable. Previously
`CCC_OVERRIDE_OPTIONS` was hardcoded.

1 files changed, 5 insertions, 4 deletions

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 6aa0f4c..87c827d 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -7204,9 +7204,10 @@ static const char *GetStableCStr(llvm::StringSet<> &SavedStrings, StringRef S) {
 ///
 ///  '#': Silence information about the changes to the command line arguments.
 ///
-///  '^': Add FOO as a new argument at the beginning of the command line.
+///  '^FOO': Add FOO as a new argument at the beginning of the command line
+///  right after the name of the compiler executable.
 ///
-///  '+': Add FOO as a new argument at the end of the command line.
+///  '+FOO': Add FOO as a new argument at the end of the command line.
 ///
 ///  's/XXX/YYY/': Substitute the regular expression XXX with YYY in the command
 ///  line.
@@ -7294,7 +7295,7 @@ static void applyOneOverrideOption(raw_ostream &OS,
 void driver::applyOverrideOptions(SmallVectorImpl<const char *> &Args,
                                   const char *OverrideStr,
                                   llvm::StringSet<> &SavedStrings,
-                                  raw_ostream *OS) {
+                                  StringRef EnvVar, raw_ostream *OS) {
   if (!OS)
     OS = &llvm::nulls();
 
@@ -7303,7 +7304,7 @@ void driver::applyOverrideOptions(SmallVectorImpl<const char *> &Args,
     OS = &llvm::nulls();
   }
 
-  *OS << "### CCC_OVERRIDE_OPTIONS: " << OverrideStr << "\n";
+  *OS << "### " << EnvVar << ": " << OverrideStr << "\n";
 
   // This does not need to be efficient.