osmo_e1f: Fix Makefile to use pkg-config

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/Makefile b/src/Makefile
index 6580c1a..cd843f8 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,5 +1,5 @@
-LDFLAGS+=-losmocore -losmogsm
-CFLAGS+=-Wall
+LDFLAGS+=`pkg-config --libs libosmocore libosmogsm`
+CFLAGS+=-Wall `pkg-config --cflags libosmocore libosmogsm`
 
 all: e1_test e1_test_dieter