[chromium-dev] Need help building anearlier checkout

[Arpit Jain]

We use webrtc for some of our code and need to update it from our last
build in mid 2016. We are planning to update our code, but first need to
get it running on our developers' systems
We have dedicated machines for building but are having trouble setting up
for development on new mac devices.
We are getting trouble on Mojave as we can't install earlier versions of
XCode (using which we know the build works )on it

Errors :
```
$ ninja -C out/Debug AppRTCDemo desktop_capture desktop_capture_differ_sse2

....
...
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSUUID.h:26:49:
error: nullability specifier '_Nullable' cannot be applied to non-pointer
type 'uuid_t' (aka 'unsigned char [16]')
- (instancetype)initWithUUIDBytes:(const uuid_t _Nullable)bytes;
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSUUID.h:29:30:
error: nullability specifier '_Nonnull' cannot be applied to non-pointer
type 'uuid_t' (aka 'unsigned char [16]')
- (void)getUUIDBytes:(uuid_t _Nonnull)uuid;
...
...
```

As per
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/fD4eSEYFR20/discussion
the suggested solution was to use SDK version 10.12 but Apple does not
allow installing this version ( .disks have newer versions of macOS )

Our build machine ( on which it works) config is
```

xcodebuild -version

Xcode 7.1.1
Build version 7B1005

sw_vers

ProductName: Mac OS X
ProductVersion: 10.13.4
BuildVersion: 17E199

gcc -v

Configured with:
--prefix=/Users/______/apps/xcode/7.1.1.app/Contents/Developer/usr
--with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.0 (clang-700.1.76)
Target: x86_64-apple-darwin17.5.0
```

Current dev configs :
```
Xcode 9.4.1
Build version 9F2000

ProductName: Mac OS X
ProductVersion: 10.14.1
BuildVersion: 18B75

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr
--with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.1.0 (clang-902.0.39.2)
Target: x86_64-apple-darwin18.2.0

```

Can anyone help be get the build running on Mojave ?
The commit id is : 302fb224a1b462b42d806a8b509122da89ad8142