Fix linking SIDE_MODULE with ports

[ryanking13]

With the removal of the RELOCATABLE flag (cfb4642), building side module with ports are not working correctly because of 1) -fPIC flag missing when building ports, and 2) pic directory not correctly passed when calculating the libdir.

Without this, building a side module that links to the port library fails with the following error:

// dummy.c
#include <emscripten/emscripten.h>
#include <jpeglib.h>

EMSCRIPTEN_KEEPALIVE
int dummy_libjpeg_smoke_test(void) {
	struct jpeg_decompress_struct cinfo;
	struct jpeg_error_mgr jerr;

	cinfo.err = jpeg_std_error(&jerr);
	jpeg_create_decompress(&cinfo);
	jpeg_destroy_decompress(&cinfo);

	return 0;
}

$ emcc dummy.c -o dummy.wasm -s USE_LIBJPEG=1 -s SIDE_MODULE=1 -ljpeg

wasm-ld: error: /home/siha/dev/temp/emscripten-regression/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libjpeg.a(jdinput.c.o): relocation R_WASM_TABLE_INDEX_SLEB cannot be used against symbol `finish_input_pass`; recompile with -fPIC
wasm-ld: error: /home/siha/dev/temp/emscripten-regression/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libjpeg.a(jdinput.c.o): relocation R_WASM_TABLE_INDEX_SLEB cannot be used against symbol `start_input_pass`; recompile with -fPIC
wasm-ld: error: /home/siha/dev/temp/emscripten-regression/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libjpeg.a(jdinput.c.o): relocation R_WASM_TABLE_INDEX_SLEB cannot be used against symbol `reset_input_controller`; recompile with -fPIC
wasm-ld: error: /home/siha/dev/temp/emscripten-regression/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libjpeg.a(jdinput.c.o): relocation R_WASM_TABLE_INDEX_SLEB cannot be used against symbol `consume_markers`; recompile with -fPIC

[sbc100]

Ha! I actually didn't know that this was some that ever worked.

[sbc100]

Can you make this into a full test that then uses the resulting side module from a main module?

[ryanking13]

Updated. How does it look now?