Makefile: use $(shell ...) to invoke pkg-config

This way the values are evaluated by make itself (not by the shell),
and can be seen in the output when running make.

Change-Id: I44db058c92377b741e24c7cdf4891ae020f37ff1
---
M src/Makefile
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/Makefile b/src/Makefile
index 3591ece..ef1c7ed 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,5 +1,5 @@
-CPPFLAGS ?= -g -O0 -Wall `pkg-config --cflags libosmocore` `pkg-config --cflags qmi-glib`
-LIBS ?= `pkg-config --libs libosmocore` `pkg-config --libs qmi-glib`
+CPPFLAGS ?= -g -O0 -Wall $(shell pkg-config --cflags libosmocore qmi-glib)
+LIBS ?= $(shell pkg-config --libs libosmocore qmi-glib)
 all: osmo-qcdiag-log
 
 MODS_LOG = gprs_l1.c gprs_rlc.o gprs_mac.o diag_gsm.o diag_log.o diag_log_gsm.o diag_log_gprs.o diag_log_wcdma.o diag_log_umts.o diag_log_qmi.o diag_dpl.o diag_log_simcard.o diag_event.o

