Fix building on MSYS2

Makefile.linux

@@ -3,13 +3,14 @@ AR       = ar
 LAUNCHER =
 RM       = rm -rf
 MKDIR    = mkdir
+ECHO     = echo
 
-LIBS= -lSDL -lpthread -L/usr/X11R6/lib -L/usr/lib -lm -lGL -lX11
-CFLAGS= -Wall -g  -I/usr/include/ -I/usr/include/SDL/ -I/usr/X11R6/include/
-LDFLAGS=
+LIBS    = -lSDL -lpthread -L/usr/X11R6/lib -L/usr/lib -lm -lGL -lX11
+CFLAGS  = -Wall -g -I/usr/include/ -I/usr/include/SDL/ -I/usr/X11R6/include/
+LDFLAGS =
 
-RES_GAMELIB=libgame.a
-RES_GAME=game
-BUILDDIR=build-linux
+RES_GAMELIB = libgame.a
+RES_GAME    = game
+BUILDDIR    = build-$(shell gcc -v 2>&1 | grep "Target:" | cut --delimiter=' ' --fields=2)
 
 include Makefile.common