android envsetup: Remove --host-os flag.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 4b254f998b37f0d32280eb85faa496f91eddfd41..8e939aff0d2b31d1fb48d9d0d513ae2c66d38f1d 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -1372,6 +1372,7 @@
              'android_sdk_version%': '<!(/bin/echo -n ${ANDROID_SDK_VERSION})',
              # Android SDK build tools (e.g. dx, aapt, aidl)
              'android_sdk_tools%': '<!(/bin/echo -n ${ANDROID_SDK_TOOLS})',
+             'host_os%': "<!(uname -s | sed -e 's/Linux/linux/;s/Darwin/mac/')",
           },
           # Copy conditionally-set variables out one scope.
           'android_ndk_root%': '<(android_ndk_root)',
@@ -1379,6 +1380,7 @@
           'android_sdk_version%': '<(android_sdk_version)',
           'android_sdk_tools%': '<(android_sdk_tools)',
           'android_stlport_root': '<(android_ndk_root)/sources/cxx-stl/stlport',
+          'host_os%': '<(host_os)',
 
           'android_sdk%': '<(android_sdk_root)/platforms/android-<(android_sdk_version)',
 
@@ -1430,6 +1432,7 @@
         'android_stlport_root': '<(android_stlport_root)',
         'android_stlport_include': '<(android_stlport_root)/stlport',
         'android_stlport_libs_dir': '<(android_stlport_root)/libs/<(android_app_abi)',
+        'host_os%': '<(host_os)',
 
         # Location of the "strip" binary, used by both gyp and scripts.
         'android_strip%' : '<!(/bin/echo -n <(android_toolchain)/*-strip)',
@@ -2074,6 +2077,9 @@
           'mac_release_optimization%': '3', # Use -O3 unless overridden
           'mac_debug_optimization%': '0',   # Use -O0 unless overridden
         }],
+        ['OS=="android"', {
+          'host_os%': '<(host_os)',  # See comment above chromium_code.
+        }],
       ],
     },
     'defines': [