[PATCH] Teach Clang how to use response files when calling other tools

[Rafael Ávila de Espíndola]

Without awk this is fine by me :-)

The idea of adding -force-response-file as a testing option would work, but I am not sure whether it is worth it or not.

Please just wait for Sean to give his OK too.

================
Comment at: test/Driver/response-file.c:17
@@ +16,3 @@
+// limit.
+// RUN: awk "BEGIN { while (count++<300000) string=string \"-DTEST \";\
+// RUN:     print string }" > %t.1.txt
----------------
My idea for using clang -E to generate the test is something like

clang -E response-gen.c | grep -v \# > %t2

with response-gen.c being

#define M -DTEST
#define M2 M M
#define M4 M2 M2
#define M8 M4 M4
#define M16 M8 M8
#define M32 M16 M16
#define M64 M32 M32
#define M128 M64 M64
#define M256 M128 M128
M256

with as many MXXX as you need.

http://reviews.llvm.org/D4897