Update README.md

Add information about Makefile in Makefile.

Author: afairon

Makefile

@@ -5,15 +5,18 @@ GOCLEAN=$(GOCMD) clean
 STRIPFLAGS=-ldflags="-s -w"
 BINARY_FILE=GitLabBack
 
+ifeq ($(GOARCH),)
+	GOARCH=amd64
+endif
+
 all: linux windows
 
 linux:
-	GOOS=$@ $(GOBUILD) $(STRIPFLAGS) -o $(BINARY_FILE)_$@
+	GOARCH=$(GOARCH) GOOS=$@ $(GOBUILD) $(STRIPFLAGS) -o $(BINARY_FILE)_$@_$(GOARCH)
 
 windows:
-	GOOS=$@ $(GOBUILD) $(STRIPFLAGS) -o $(BINARY_FILE)_$@
+	GOARCH=$(GOARCH) GOOS=$@ $(GOBUILD) $(STRIPFLAGS) -o $(BINARY_FILE)_$@_$(GOARCH)
 
 clean:
 	$(GOCLEAN)
-	rm -f $(BINARY_FILE)_linux
-	rm -f $(BINARY_FILE)_windows
+	rm -f $(BINARY_FILE)_*

README.md

@@ -18,7 +18,7 @@ $ ./GitLabBack
 $ ./GitLabBack -h
 Usage of GitLabBack:
   -config string
-        Config path (default ".GitLabBack.json")
+        Config path (default "~/.gitlabback")
   -dir string
         Backup directory
   -ssh
@@ -31,7 +31,12 @@ Usage of GitLabBack:
 
 ## Configuration
 
-Default configuration file is ".GitLabBack.json".
+Default configuration file is ".gitlabback".
+
+- baseURL Link to GitLab server (default: https://gitlab.com/)
+- token Private token
+- backupdir Your backup directory
+- ssh Clone with ssh (token is not needed)
 
 ```json
 {"baseURL":"","token":"YOUR TOKEN","backupdir":"","ssh":false}
@@ -44,3 +49,18 @@ If you have Golang 1.11.x+ installed, you can clone the repository and:
 ```bash
 $ go build
 ```
+
+To ease the compilation process, the developer can use the provided Makefile.
+
+```bash
+$ make                    # builds for linux and windows
+$ make linux              # builds for linux
+$ make windows            # builds for windows
+$ GOARCH=arm64 make linux # builds for arm64 linux
+```
+
+Start off from fresh build.
+
+```bash
+$ make clean # removes go binaries
+```