MIPS64: Add support for architecture revision 6.

build/toolchain.gypi

Index: build/toolchain.gypi
diff --git a/build/toolchain.gypi b/build/toolchain.gypi
index e1b533d4dcc1fca757a474c3c396f6772a9b40e6..4e07770160ebfc21a6f0abedd7d51d627429909e 100644
--- a/build/toolchain.gypi
+++ b/build/toolchain.gypi
@@ -376,6 +376,14 @@
                     'cflags': ['-msoft-float'],
                     'ldflags': ['-msoft-float'],
                   }],
+                  ['mips_arch_variant=="r6"', {
+                    'cflags': ['-mips64r6', '-mabi=64', '-Wa,-mips64r6'],
+                    'ldflags': [
+                      '-mips64r6', '-mabi=64',
+                      '-Wl,--dynamic-linker=$(LDSO_PATH)',
+                      '-Wl,--rpath=$(LD_R_PATH)',
+                    ],
+                  }],
                   ['mips_arch_variant=="r2"', {
                     'cflags': ['-mips64r2', '-mabi=64', '-Wa,-mips64r2'],
                     'ldflags': [
@@ -406,6 +414,9 @@
               '__mips_soft_float=1'
             ],
           }],
+          ['mips_arch_variant=="r6"', {
+            'defines': ['_MIPS_ARCH_MIPS64R6',],
+          }],
           ['mips_arch_variant=="r2"', {
             'defines': ['_MIPS_ARCH_MIPS64R2',],
           }],