dnsdist picks up cdb.h but can't link in the static archive.

/home/sk/tmp/openwrt/staging_dir/toolchain-mips_24kc_gcc-8.3.0_musl/lib/gcc/mips-openwrt-linux-musl/8.3.0/../../../../mips-openwrt-linux-musl/bin/ld: /home/sk/tmp/openwrt/staging_dir/target-mips_24kc_musl/usr/lib/libcdb.a(cdb_init.o): relocation R_MIPS_26 against `fstat' can not be used when making a shared object; recompile with -fPIC

This commit extends the tinycdb Makefile to build and install as well
the shared library as well as the pic archive. dnsdist will then pick
the shared library.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>