Add "(compatible with GNU linkers)" to the lld version output to avoid

problems with configure scripts generated with libtool.m4 that would
otherwise have to be regenerated with a patched libtool.

Among other things this fixes the build of Mesa on arm64 with lld.

From lld svn revision 298532.  ok kettenis@

1 files changed, 20 insertions, 4 deletions

diff --git a/gnu/llvm/tools/lld/ELF/Driver.cpp b/gnu/llvm/tools/lld/ELF/Driver.cpp
index 3cf88e3c1ca..99253313c35 100644
--- a/gnu/llvm/tools/lld/ELF/Driver.cpp
+++ b/gnu/llvm/tools/lld/ELF/Driver.cpp
@@ -281,11 +281,27 @@ void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) {
     return;
   }
 
-  // GNU linkers disagree here. Though both -version and -v are mentioned
-  // in help to print the version information, GNU ld just normally exits,
-  // while gold can continue linking. We are compatible with ld.bfd here.
+  // Handle -v or -version.
+  //
+  // A note about "compatible with GNU linkers" message: this is a hack for
+  // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
+  // still the newest version in March 2017) or earlier to recognize LLD as
+  // a GNU compatible linker. As long as an output for the -v option
+  // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
+  //
+  // This is somewhat ugly hack, but in reality, we had no choice other
+  // than doing this. Considering the very long release cycle of Libtool,
+  // it is not easy to improve it to recognize LLD as a GNU compatible
+  // linker in a timely manner. Even if we can make it, there are still a
+  // lot of "configure" scripts out there that are generated by old version
+  // of Libtool. We cannot convince every software developer to migrate to
+  // the latest version and re-generate scripts. So we have this hack.
   if (Args.hasArg(OPT_version) || Args.hasArg(OPT_v))
-    outs() << getLLDVersion() << "\n";
+    outs() << getLLDVersion() << " (compatible with GNU linkers)\n";
+
+  // ld.bfd always exits after printing out the version string.
+  // ld.gold proceeds if a given option is -v. Because gold's behavior
+  // is more permissive than ld.bfd, we chose what gold does here.
   if (Args.hasArg(OPT_version))
     return;