sr: fix conditional build for ezusb and serial helpers

configure.ac

@@ -247,6 +247,18 @@ if test "x$LA_ALSA" != xno; then
 		SR_PKGLIBS="$SR_PKGLIBS alsa"])
 fi
 
+# EZUSB FX2 firmware helpers only needed for some hardware drivers
+AM_CONDITIONAL(NEED_EZUSB, \
+	test "x$LA_FX2LAFW" != xno \
+	-o "x$HW_HANTEK_DSO" != xno \
+)
+
+# Serial port helpers only needed for some hardware drivers
+AM_CONDITIONAL(NEED_SERIAL, \
+	test "x$LA_OLS" != xno \
+	-o "x$HW_GENERICDMM" != xno \
+)
+
 AC_SUBST(SR_PKGLIBS)
 
 # Checks for header files.

hardware/common/Makefile.am

@@ -22,11 +22,11 @@ noinst_LTLIBRARIES = libsigrokhwcommon.la
 
 libsigrokhwcommon_la_SOURCES =
 
-if LA_FX2LAFW
+if NEED_EZUSB
 libsigrokhwcommon_la_SOURCES += ezusb.c
 endif
 
-if LA_OLS
+if NEED_SERIAL
 libsigrokhwcommon_la_SOURCES += serial.c
 endif