[mips] Recognise the triple used by Debian for MIPS n32 ABI

Triples like mips64-linux-gnuabin32 are documented in this article:
https://wiki.debian.org/Multiarch/Tuples

llvm-svn: 313231
diff --git a/llvm/lib/Support/Triple.cpp b/llvm/lib/Support/Triple.cpp
index 73dc59c..8dc582a 100644
--- a/llvm/lib/Support/Triple.cpp
+++ b/llvm/lib/Support/Triple.cpp
@@ -216,6 +216,7 @@
   switch (Kind) {
   case UnknownEnvironment: return "unknown";
   case GNU: return "gnu";
+  case GNUABIN32: return "gnuabin32";
   case GNUABI64: return "gnuabi64";
   case GNUEABIHF: return "gnueabihf";
   case GNUEABI: return "gnueabi";
@@ -505,6 +506,7 @@
   return StringSwitch<Triple::EnvironmentType>(EnvironmentName)
     .StartsWith("eabihf", Triple::EABIHF)
     .StartsWith("eabi", Triple::EABI)
+    .StartsWith("gnuabin32", Triple::GNUABIN32)
     .StartsWith("gnuabi64", Triple::GNUABI64)
     .StartsWith("gnueabihf", Triple::GNUEABIHF)
     .StartsWith("gnueabi", Triple::GNUEABI)