The log shows many compilation errors starting with:
:info:destroot /System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:19:21: error: expected a type
:info:destroot - (id)copyWithZone:(nullable NSZone *)zone;
:info:destroot ^
:info:destroot /System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:25:28: error: expected a type
:info:destroot - (id)mutableCopyWithZone:(nullable NSZone *)zone;
:info:destroot ^
It also shows that your clang version is 600.0.57. According to XcodeVersionInfo, that's from Xcode 6.2. That's too old to be compatible with El Capitan. You need to upgrade to Xcode 7 or later. If you've upgraded to El Capitan from a previous OS X version, make sure you've followed all the steps in wiki:Migration. Upgrading Xcode is step 1.