fix the SKIP builddir directive

Change-Id: I3e1c5bd61ac952be00fd6a6961fed1a7992d3bad
Prefer const char[] over const char* const were possible.

The first ends up in the .rodata section, the latter in .data.rel.ro.

Change-Id: I8545aa15de4b84dd4d96bc28fe725db4f7d40af2