Use -gdwarf-3 by default, -gdwarf-4 if dwarf4=1 option is passed to make.

Makefile

@@ -33,6 +33,10 @@
 #
 #   Unit test target: unittests
 #
+# Options
+#
+#   dwarf4=1 - use DWARF v4 format for debug information
+#
 
 export TARGET_MODES = debug debug_release release
 export TARGET_PC_SYSTEMS = linux
@@ -48,6 +52,8 @@ export FLASH_TARGETS = $(foreach __TARGET,$(foreach __MODE,$(TARGET_MODES),$(for
 export OUT_DIR = ./out
 export UNITTESTS_SRC_DIR = ./tests/unit
 
+export dwarf4
+
 all: clean $(JERRY_TARGETS) $(TESTS_TARGET) $(CHECK_TARGETS)
 
 $(JERRY_TARGETS) $(TESTS_TARGET) $(FLASH_TARGETS) $(CHECK_TARGETS):