Updated Compile and install on macOS using macports (markdown)

Compile-and-install-on-macOS-using-macports.md

@@ -19,6 +19,8 @@ Install dependencies through port:
 
 Install create-dmg:
 
+    mkdir -p ~/build
+    cd ~/build
     git clone https://github.com/create-dmg/create-dmg
     cd create-dmg
     sudo make install
@@ -31,6 +33,8 @@ Set environment variables:
 
 Get code, compile and create DMG:
 
+    mkdir -p ~/build
+    cd ~/build
     git clone https://github.com/strawberrymusicplayer/strawberry
     cd strawberry
     mkdir build