AIX: Define __STDC_FORMAT_MACROS in gypi file

    Some system header files on AIX include inttypes.h without
    defining __STDC_FORMAT_MACROS and therefore the printf format
    specifier macro (for eg. PRId64) doesn't get defined as they
    are guarded with __STDC_FORMAT_MACROS macro on AIX.
    This error showed up recently when the format specifier was used in
    wasm-interpreter.cc, where a AIX system header file is included
    which also includes inttypes.h without defining __STDC_FORMAT_MACROS.

R=ahaas@chromium.org, titzer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2033483002
Cr-Commit-Position: refs/heads/master@{#36682}

gypfiles/toolchain.gypi

@@ -1089,6 +1089,7 @@
         'defines': [
           # Support for malloc(0)
           '_LINUX_SOURCE_COMPAT=1',
+          '__STDC_FORMAT_MACROS',
           '_ALL_SOURCE=1'],
         'conditions': [
           [ 'v8_target_arch=="ppc"', {