initial cache-key resolution should display whole key, not just a short SHA

Current log is as below. The short shas can't used as a definitive list of what was being built. reviewing this log much later on big projects, we'd be at risk of finding clashes.

fetch needed 20b0640d gnu-toolchain/base.bst 
fetch needed b57571d4 gnu-toolchain/stage1-binutils.bst 
fetch needed 2d81f140 gnu-toolchain/stage1-gcc.bst 
     waiting 15871240 gnu-toolchain/stage1.bst 
fetch needed 1c5173b0 gnu-toolchain/stage2-fhs-dirs.bst 
fetch needed 238d8701 gnu-toolchain/stage2-linux-api-headers.bst 
fetch needed 78eddec5 gnu-toolchain/stage2-glibc.bst 
fetch needed 72aa4f3b gnu-toolchain/stage2-binutils.bst 
fetch needed dbb0b7ba gnu-toolchain/stage2-busybox.bst 
     waiting a4774fa2 gnu-toolchain/stage2-fake-bash.bst 
fetch needed 3e3f53d0 gnu-toolchain/stage2-gawk.bst 
fetch needed 61c71f36 gnu-toolchain/stage2-gcc-fixed-headers.bst 
fetch needed 8617fec8 gnu-toolchain/stage2-libstdcxx.bst 
fetch needed 1eb11709 gnu-toolchain/stage2-gcc.bst 
fetch needed af38df08 gnu-toolchain/stage2-make.bst 
     waiting c0ac6a25 gnu-toolchain/stage2-reset-specs.bst 
     waiting 362f602b gnu-toolchain/stage2.bst 
fetch needed 495cfcd4 gnu-toolchain/fhs-dirs.bst 
fetch needed 437eae39 gnu-toolchain/linux-api-headers.bst 
fetch needed d0efee0f gnu-toolchain/glibc.bst 
fetch needed fb9edf71 gnu-toolchain/zlib.bst 
fetch needed f3bc509b gnu-toolchain/binutils.bst 
fetch needed bb8dfc34 gnu-toolchain/busybox.bst 
fetch needed 75a98368 gnu-toolchain/ccache.bst 
fetch needed 41117f13 gnu-toolchain/gawk.bst 
fetch needed f414eabf gnu-toolchain/m4-tarball.bst 
fetch needed 75a261c6 gnu-toolchain/gcc.bst