Don't export CC

This was causing cmake to double-invoke ccache for compilation units,
and broke oxen-mq's local zmq build for the same reason.

.drone.jsonnet

@@ -104,16 +104,15 @@ local local_gnutls(jobs=6, prefix='/usr/local') = [
   apt_get_quiet + ' install -y curl ca-certificates',
   'curl -sSL https://ftp.gnu.org/gnu/nettle/nettle-3.9.1.tar.gz | tar xfz -',
   'curl -sSL https://www.gnupg.org/ftp/gcrypt/gnutls/v3.8/gnutls-3.8.0.tar.xz | tar xfJ -',
-  'export CC="ccache gcc"',
   'export PKG_CONFIG_PATH=' + prefix + '/lib/pkgconfig:' + prefix + '/lib64/pkgconfig',
   'export LD_LIBRARY_PATH=' + prefix + '/lib:' + prefix + '/lib64',
   'cd nettle-3.9.1',
-  './configure --prefix=' + prefix,
+  './configure --prefix=' + prefix + ' CC="ccache gcc"',
   'make -j' + jobs,
   'make install',
   'cd ..',
   'cd gnutls-3.8.0',
-  './configure --prefix=' + prefix + ' --with-included-libtasn1 --with-included-unistring --without-p11-kit  --disable-libdane --disable-cxx --without-tpm --without-tpm2',
+  './configure --prefix=' + prefix + ' --with-included-libtasn1 --with-included-unistring --without-p11-kit  --disable-libdane --disable-cxx --without-tpm --without-tpm2 CC="ccache gcc"',
   'make -j' + jobs,
   'make install',
   'cd ..',