[Triple] Add "swift" as a vendor.

We want this so we can uniquely identify our fully-static Linux
target using a triple (since we wish to make decisions about it in
the compiler driver that wouldn't be appropriate for an "unknown"
triple).

rdar://123436421
(cherry picked from commit 18ba856)

Author: al45tair

llvm/include/llvm/TargetParser/Triple.h

@@ -194,7 +194,8 @@ class Triple {
     Mesa,
     SUSE,
     OpenEmbedded,
-    LastVendorType = OpenEmbedded
+    Swift,
+    LastVendorType = Swift
   };
   enum OSType {
     UnknownOS,

llvm/lib/TargetParser/Triple.cpp

@@ -253,6 +253,7 @@ StringRef Triple::getVendorTypeName(VendorType Kind) {
   case PC: return "pc";
   case SCEI: return "scei";
   case SUSE: return "suse";
+  case Swift: return "swift";
   }
 
   llvm_unreachable("Invalid VendorType!");
@@ -634,6 +635,7 @@ static Triple::VendorType parseVendor(StringRef VendorName) {
     .Case("amd", Triple::AMD)
     .Case("mesa", Triple::Mesa)
     .Case("suse", Triple::SUSE)
+    .Case("swift", Triple::Swift)
     .Case("oe", Triple::OpenEmbedded)
     .Default(Triple::UnknownVendor);
 }