ios: Fixing base_unittests to build with gn.

build/secondary/third_party/nss/BUILD.gn

Index: build/secondary/third_party/nss/BUILD.gn
diff --git a/build/secondary/third_party/nss/BUILD.gn b/build/secondary/third_party/nss/BUILD.gn
index e51fb21ac62595f27d9ade6b265e06bafeb32619..64d6e88ad688e79058533c8026c5abdef6862e93 100644
--- a/build/secondary/third_party/nss/BUILD.gn
+++ b/build/secondary/third_party/nss/BUILD.gn
@@ -1096,7 +1096,7 @@ if (is_linux) {
       defines += [ "NSS_DISABLE_ROOT_CERTS" ]
     }
 
-    if (current_cpu == "x64" && !is_win) {
+    if (current_cpu == "x64" && !is_win && !is_ios) {
       sources -= [
         "nss/lib/freebl/chacha20/chacha20.c",
         "nss/lib/freebl/poly1305/poly1305.c",
@@ -1177,6 +1177,9 @@ if (is_linux) {
         # mpi_x86_asm.c contains MSVC inline assembly code.
         "nss/lib/freebl/mpi/mpi_x86_asm.c",
       ]
+      if (is_ios) {
+        sources -= [ "nss/lib/freebl/intel-aes-x86-masm.asm" ]

[Nico, 2015/08/18 15:15:43]

Shouldn't .asm files be ignored automatically on non-Win? Why is this needed for
ios but not other platforms?

[sherouk, 2015/08/18 16:06:23]

No, they are not filtered. This target is only defined on Win, Mac and iOS not
linux. Mac build is not supported by GN yet  

[Nico, 2015/08/18 17:47:05]

There's a main waterfall bot doing GN bots on OS X:
http://build.chromium.org/p/chromium.mac/builders/Mac%20GN%20%28dbg%29/builds...
It builds base_unittests fine.

[sherouk, 2015/08/19 13:14:32]

I was not aware of that bot, Thanks! This bot doesn't build third part nss
because it's not a dependency of base. Do i have to change the condition to be
if(is_ios || is_mac) or i have to remove the condition?

[Nico, 2015/08/19 15:28:05]

Ah, iOS is the only platform we still build NSS on, the rest is on borgingssl by
now, right.. The gyp file seems to unconditionally remove this file on !is_win
(which is already true in this block), so I'd just do this. (i.e. remove the "if
is_ios" line)

In general, looking at the gyp files and doing what's done there where it makes
sense is a good pattern, as the gyp build is known to work.

[sherouk, 2015/08/19 16:50:08]

Done, Thank you!

+      }
     }
 
     if (is_clang) {