Workaround for false -Warray-bounds in Travis
Workaround for false -Warray-bounds in Travis

ccache + clang produces a false strcmp warning, see
https://llvm.org/bugs/show_bug.cgi?id=20144

Since this only happens with ccache and --strict-warnings, and
only with certain versions of glibc / clang, disabling
ccache is a reasonable short-term workaround.

Reviewed-by: Richard Levitte <5fb523282dd7956571c80524edc2dccfa0bd8234@openssl.org>

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl