Fix build failure for test programs on gcc-10 (#1464)
Fix build failure for test programs on gcc-10 (#1464)

Previously, gcc (Debian 10.2.1-6) 10.2.1 20210110 gave the following
error message:

/usr/bin/ld: tests/util.o:(.data+0x0): multiple definition of `matches_blob_uses_default_iterator'; tests/test-arena.o:(.bss+0x0): first defined here
cblichmann/yara,cblichmann/yara,cblichmann/yara,cblichmann/yara,cblichmann/yara