[clang] [Basic] Define time64 macros for *t64 triples

Set the `-D_FILE_OFFSET_BITS=64` and `-D_TIME_BITS=64` defaults when
clang is builting for one of the `*t64` triples that Gentoo is planning
to use for 32-bit platforms migrated to 64-bit time_t.

Author: mgorny

clang/lib/Basic/Targets/OSTargets.h

@@ -337,6 +337,10 @@ class LLVM_LIBRARY_VISIBILITY LinuxTargetInfo : public OSTargetInfo<Target> {
       Builder.defineMacro("_GNU_SOURCE");
     if (this->HasFloat128)
       Builder.defineMacro("__FLOAT128__");
+    if (Triple.isTime64ABI()) {
+      Builder.defineMacro("_FILE_OFFSET_BITS", "64");
+      Builder.defineMacro("_TIME_BITS", "64");
+    }
   }
 
 public:

clang/test/Preprocessor/time64.c

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -E -dM -triple=i686-pc-linux-gnu /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=i686-pc-linux-gnut64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+// RUN: %clang_cc1 -E -dM -triple=armv5tel-softfloat-linux-gnueabi /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=armv5tel-softfloat-linux-gnueabit64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+// RUN: %clang_cc1 -E -dM -triple=armv7a-unknown-linux-gnueabihf /dev/null | FileCheck -match-full-lines -check-prefix TIME32 %s
+// RUN: %clang_cc1 -E -dM -triple=armv7a-unknown-linux-gnueabihft64 /dev/null | FileCheck -match-full-lines -check-prefix TIME64 %s
+//
+// TIME32-NOT:#define _FILE_OFFSET_BITS 64
+// TIME32-NOT:#define _TIME_BITS 64
+//
+// TIME64:#define _FILE_OFFSET_BITS 64
+// TIME64:#define _TIME_BITS 64