autoconf-archive-2019.01.06 breaks AX_CODE_COVERAGE usage by requiring
a different integration inside Makefile.am. This would be fine if the
local m4/ax_code_coverage.m4 would get used, but eaclocal parses out
the install from ACLOCAL_AMFLAGS, and calls aclocal with that, which
overwrites ax_code_coverage.m4 with the newer version, obviously
breaking the usage of all that in Makefile.am.
Workaround it by patching out the --install argument, thus using the
tarball copy of it (older version), which works with Makefile.am
without further patching.

--- a/Makefile.am
+++ b/Makefile.am
@@ -1,6 +1,6 @@
 SUBDIRS = . po docs gdata/tests
 
-ACLOCAL_AMFLAGS = --install -I m4 ${ACLOCAL_FLAGS}
+ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
 
 DISTCHECK_CONFIGURE_FLAGS =
 MAINTAINERCLEANFILES =