[build] Only required dependencies for enabled components

This makes sure we only pkg require dependencies for enabled components.

Note this has not been tested on a system that uses SSU, meegolock and
sailfish-access-control. systemd has been tested

configure.ac

@@ -105,10 +105,30 @@ PKG_CHECK_MODULES([USB_MODED], [
  gio-2.0
  libudev
  libkmod
- ssu-sysinfo
- libsystemd
- dsme
- sailfishaccesscontrol
+])
+
+AS_IF([test "x$mer_ssu" = "xtrue"], [
+   PKG_CHECK_MODULES([SSU_SYSINFO], [ssu-sysinfo])
+   AC_SUBST(SSU_SYSINFO_LIBS)
+   AC_SUBST(SSU_SYSINFO_CFLAGS)
+])
+
+AS_IF([test "x$meegodevlock" = "xtrue"], [
+   PKG_CHECK_MODULES([DSME], [dsme])
+   AC_SUBST(DSME_LIBS)
+   AC_SUBST(DSME_CFLAGS)
+])
+
+AS_IF([test "x$sailfish_access_control" = "xtrue"], [
+   PKG_CHECK_MODULES([SAILFISH_ACCESS_CONTROL], [sailfishaccesscontrol])
+   AC_SUBST(SAILFISH_ACCESS_CONTROLD_LIBS)
+   AC_SUBST(SAILFISH_ACCESS_CONTROL_CFLAGS)
+])
+
+AS_IF([test "x$systemd" = "xtrue"], [
+   PKG_CHECK_MODULES([SYSTEMD], [libsystemd])
+   AC_SUBST(SYSTEMD_LIBS)
+   AC_SUBST(SYSTEMD_CFLAGS)
 ])
 
 AC_SUBST(USB_MODED_LIBS)

src/Makefile.am

@@ -55,6 +55,9 @@ if USE_MER_SSU
 usb_moded_SOURCES += \
 	usb_moded-ssu.h \
 	usb_moded-ssu.c
+
+usb_moded_CPPFLAGS += ${SSU_SYSINFO_CFLAGS}
+usb_moded_LDADD += ${SSU_SYSINFO_LIBS}
 endif
 
 if MEEGOLOCK
@@ -63,6 +66,9 @@ usb_moded_SOURCES += \
 	usb_moded-devicelock.c \
 	usb_moded-dsme.h \
 	usb_moded-dsme.c
+
+usb_moded_CPPFLAGS += ${DSME_CFLAGS}
+usb_moded_LDADD += ${DSME_LIBS}
 endif
 
 if APP_SYNC
@@ -81,8 +87,13 @@ usb_moded_SOURCES += \
 endif
 
 if SAILFISH_ACCESS_CONTROL
-usb_moded_CPPFLAGS += `pkg-config --cflags sailfishaccesscontrol`
-usb_moded_LDFLAGS  += `pkg-config --libs sailfishaccesscontrol`
+usb_moded_CPPFLAGS += ${SAILFISH_ACCESS_CONTROL_CFLAGS}
+usb_moded_LDADD  += ${SAILFISH_ACCESS_CONTROL_LIBS}
+endif
+
+if SYSTEMD
+usb_moded_CPPFLAGS += ${SYSTEMD_CFLAGS}
+usb_moded_LDADD += ${SYSTEMD_LIBS}
 endif
 
 usb_moded_util_CPPFLAGS = \