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
```
issue