tests: USE_CCACHE on host system results in test failures

Few of the tests expect the dependencies to already be installed on the host. Because of this, when using USE_CCACHE in the host's abuild.conf, the tests fail.

abuild check() output

 ✗ abuild: build simple package without deps
   (in test file abuild.bats, line 21)
     `$ABUILD' failed
   >>> pkg1: Building testrepo/pkg1 1.0-r0 (using abuild 3.7.0_rc1-r0) started Sat, 28 Nov 2020 11:18:20 +0000
   >>> pkg1: Checking sanity of /home/caskd/Packages/misc-tools/abuild/src/abuild-3.7.0_rc1/tests/testrepo/pkg1/APKBUILD...
   >>> pkg1: Analyzing dependencies...
   >>> ERROR: pkg1: Missing dependencies (use -r to autoinstall them):  ccache
   >>> ERROR: pkg1: builddeps failed
 ✓ abuild: build failure
 ✓ abuild: test check for /usr/lib64
 ✗ abuild: test options=lib64
   (in test file abuild.bats, line 38)
     `options=lib64 $ABUILD' failed
   >>> lib64test: Building testrepo/lib64test 1.0-r0 (using abuild 3.7.0_rc1-r0) started Sat, 28 Nov 2020 11:18:20 +0000
   >>> lib64test: Checking sanity of /home/caskd/Packages/misc-tools/abuild/src/abuild-3.7.0_rc1/tests/testrepo/lib64test/APKBUILD...
   >>> lib64test: Analyzing dependencies...
   >>> ERROR: lib64test: Missing dependencies (use -r to autoinstall them):  ccache
   >>> ERROR: lib64test: builddeps failed
 ✗ abuild: verify that packages are reproducible built
   (in test file abuild.bats, line 47)
     `$ABUILD' failed
   >>> pkg1: Building testrepo/pkg1 1.0-r0 (using abuild 3.7.0_rc1-r0) started Sat, 28 Nov 2020 11:18:20 +0000
   >>> pkg1: Checking sanity of /home/caskd/Packages/misc-tools/abuild/src/abuild-3.7.0_rc1/tests/testrepo/pkg1/APKBUILD...
   >>> pkg1: Analyzing dependencies...
   >>> ERROR: pkg1: Missing dependencies (use -r to autoinstall them):  ccache
   >>> ERROR: pkg1: builddeps failed

References: https://gitlab.alpinelinux.org/alpine/abuild/-/blob/master/tests/abuild.bats#L21