tools: libressl: always build as PIC

Fixes link errors for host packages like ruby like the following:

/usr/bin/ld: .../staging_dir/host/lib/libcrypto.a(libcrypto_la-md5_dgst.o):
relocation R_X86_64_PC32 against symbol `memcpy@@GLIBC_2.14' can not be used when making a shared object; recompile with -fPIC

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

tools/libressl/Makefile

@@ -22,5 +22,6 @@ HOST_BUILD_PARALLEL:=1
 include $(INCLUDE_DIR)/host-build.mk
 
 HOST_CONFIGURE_ARGS += --disable-shared
+HOST_CFLAGS += $(FPIC)
 
 $(eval $(call HostBuild))