package/mender/mender.mk: fix linker version argument

The current linker flag "-X main.Version=$(MENDER_VERSION)" no longer points
to the correct location, which results in "version: unknown" when runnning
"mender -version." Update the linker flag to point to the correct location.

Signed-off-by: Adam Duskett <Aduskett@rivian.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit b5f7fa88381e3a4aa0e6c1e567dd5f164de176ba)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/mender/mender.mk

@@ -35,7 +35,7 @@ MENDER_LICENSE_FILES = \
 
 MENDER_DEPENDENCIES = xz
 
-MENDER_LDFLAGS = -X main.Version=$(MENDER_VERSION)
+MENDER_LDFLAGS = -X github.com/mendersoftware/mender/conf.Version=$(MENDER_VERSION)
 
 MENDER_UPDATE_MODULES_FILES = \
 	directory \