Make it possible to change gobin

Makefile

@@ -1,32 +1,35 @@
-# Constant variables for simplifying code below.
-appID=com.github.jacalz.sparta
-icon=internal/assets/icon-512.png
-name=Sparta
+# Constants for cross compilation and packaging.
+appID = com.github.jacalz.sparta
+icon = internal/assets/icon-512.png
+name = Sparta
+
+# Default path to the go binary directory.
+GOBIN ?= ~/go/bin/
 
 bundle:
 	# Bundle the correct logo into sparta/src/bundled/bundled.go
-	~/go/bin/fyne bundle -package assets internal/assets/icon-256.png > internal/assets/bundled.go
+	${GOBIN}fyne bundle -package assets internal/assets/icon-256.png > internal/assets/bundled.go
 
 	# Modify the variable name to be correct.
 	sed -i 's/resourceIcon256Png/AppIcon/g' internal/assets/bundled.go
 
 check:
 	# Check the whole codebase for misspellings.
-	~/go/bin/misspell -w .
+	${GOBIN}misspell -w .
 
 	# Run full formating on the code.
 	gofmt -s -w .
 
 	# Check the whole program for security issues.
-	~/go/bin/gosec ./...
+	${GOBIN}gosec ./...
 
 darwin:
-	~/go/bin/fyne-cross darwin -arch amd64 -app-id ${appID} -icon ${icon} -output ${name}
+	${GOBIN}fyne-cross darwin -arch amd64 -app-id ${appID} -icon ${icon} -output ${name}
 
 linux:
-	~/go/bin/fyne-cross linux -arch amd64 -app-id ${appID} -icon ${icon}
+	${GOBIN}fyne-cross linux -arch amd64 -app-id ${appID} -icon ${icon}
 
 windows:
-	~/go/bin/fyne-cross windows -arch amd64 -app-id ${appID} -icon ${icon}
+	${GOBIN}fyne-cross windows -arch amd64 -app-id ${appID} -icon ${icon}
 
 cross-compile: darwin linux windows