libvpx.gyp : issues fix for webview.

Use the new gyp_var_prefix local variable set by gyp instead of the
global GYP_VAR_PREFIX set by the makefiles, since the latter is not
guaranteed to still be the same value at the time the command is
executed. Also, use abspath instead of realpath to convert paths to
absolute, since realpath expands to the empty string if the target file
doesn't exist, complicating build debugging.

Removed 2 include paths from WebView build, they are not used in WebView,
  but generate full path which shouldn't in android make file.

BUG=
R=johannkoenig@google.com, torne@chromium.org

Committed: 271093

[Johann, 2014-05-16 04:15:58]

Would prefer to see the comment cleaned up and the places where cflags are
modified kept together.

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp#newcode359
libvpx.gyp:359: 'cflags': [
would prefer to keep the chunks that modify cflags together. This could be moved
up or the other directive could be moved down.

# Add include paths for assembler:
cflags[...]
# For android webview, the following paths are not required and not allowed:
webview!=1[...]

I believe the reason for some of these paths were os x clang searched
differently than other versions we were using. But this isn't under
xcode_settings so I may be misremembering.

[Torne, 2014-05-16 09:50:07]

LGTM from webview build perspective (this is the change we need and I've tested
it works). Hopefully this is the final iteration of this; sorry for the
inconvenience, people kept reporting more configurations I hadn't tested :/

[Tom Finegan, 2014-05-16 17:40:21]

On 2014/05/16 09:50:07, Torne wrote:
> LGTM from webview build perspective (this is the change we need and I've
tested
> it works). Hopefully this is the final iteration of this; sorry for the
> inconvenience, people kept reporting more configurations I hadn't tested :/

+1 on Johann's comment. Looks fine otherwise.

[michaelbai, 2014-05-16 18:09:00]

PTAL

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp#newcode359
libvpx.gyp:359: 'cflags': [
xcode_settings has same setting in line 291,  and
Do you know why the path leads with comma?


On 2014/05/16 04:15:58, Johann wrote:
> would prefer to keep the chunks that modify cflags together. This could be
moved
> up or the other directive could be moved down.
> 
> # Add include paths for assembler:
> cflags[...]
> # For android webview, the following paths are not required and not allowed:
> webview!=1[...]
> 
> I believe the reason for some of these paths were os x clang searched
> differently than other versions we were using. But this isn't under
> xcode_settings so I may be misremembering.

[Johann, 2014-05-16 18:25:31]

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp#newcode359
libvpx.gyp:359: 'cflags': [
On 2014/05/16 18:09:00, michaelbai wrote:
> xcode_settings has same setting in line 291,  and

All the more reason to keep these modification close to each other

> Do you know why the path leads with comma?

the , trailing -Wa and -I? I do not know what that means.

[michaelbai, 2014-05-16 19:57:31]

PTAL

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp#newcode359
libvpx.gyp:359: 'cflags': [
Put them together


On 2014/05/16 18:25:31, Johann wrote:
> On 2014/05/16 18:09:00, michaelbai wrote:
> > xcode_settings has same setting in line 291,  and
> 
> All the more reason to keep these modification close to each other
> 
> > Do you know why the path leads with comma?
> 
> the , trailing -Wa and -I? I do not know what that means.

[Johann, 2014-05-16 21:03:09]

lgtm. i'm working on a roll, i'll carry this in hopefully today

[michaelbai, 2014-05-16 21:08:51]

Committed patchset #2 manually as r271093 (presubmit successful).

[Torne, 2014-05-19 09:02:09]

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/288293002/diff/40001/libvpx.gyp#newcode359
libvpx.gyp:359: 'cflags': [
On 2014/05/16 18:25:31, Johann wrote:
> On 2014/05/16 18:09:00, michaelbai wrote:
> > Do you know why the path leads with comma?
> 
> the , trailing -Wa and -I? I do not know what that means.

-Wa is the gcc option for passing arguments to the assembler. The commas
separate the different arguments to pass to the assembler, so that it can tell
the difference between you wanting to pass N assembler arguments from you
wanting to pass, say, N-1 assembler arguments and 1 other gcc argument. So,
-Wa,-I,foo means "pass the arguments -I and foo to the assembler". Without the
commas gcc would attempt to interpret the -I and foo args itself.