fix(build): don't rely on that gcc-ar is in the same directory as gcc

ccache - a fast C/C++ compiler cache.
ccache wraps gcc and g++ compilers, but not other tools like ar.
If ccache is installed, then build fails with

```
make: /usr/lib/ccache/aarch64-linux-gnu-gcc-ar: No such file or directory
```

Change-Id: I555c178aeaa0cf411cdf67b4a81e7952be762d0f
Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed