external_deps: disable -fpic when building nettle, we already use -fPIC

This avoids this error when linking the linux-arm64 engine:

libnettle.a(buffer-init.o): in function `nettle_buffer_init': (.text+0x8): relocation truncated to fit:
  R_AARCH64_LD64_GOTPAGE_LO15 against symbol `nettle_realloc' defined in .text section in libnettle.a(realloc.o)
/usr/aarch64-linux-gnu/bin/ld: (.text+0x8): warning: too many GOT entries for -fpic, please recompile with -fPIC

Author: illwieckz

external_deps/build.sh

@@ -370,7 +370,8 @@ build_nettle() {
 	cd "${dir_name}"
 
 	configure_build \
-		--disable-fat
+		--disable-fat \
+		--disable-pic
 }
 
 # Build cURL