[tools/cmx] fix test flake

Valico isn't consistent in the ordering of error messages, so sort
errors before assembling the final message such that tests have reliable
output.

TEST: while [ 0 -eq $? ]; do ./out/x64/host_x64/cmx_bin_test_rustc; done
Change-Id: I96897ee42344afd9dd2c2e473c1bb6488ada20f5
1 file changed