Fix compiling lcc using mingw under cygwin

Also have 'make' under cygwin automatically use mingw.

Makefile

@@ -52,6 +52,10 @@ endif
 #############################################################################
 -include Makefile.local
 
+ifeq ($(COMPILE_PLATFORM),cygwin)
+  PLATFORM=mingw32
+endif
+
 ifndef PLATFORM
 PLATFORM=$(COMPILE_PLATFORM)
 endif
@@ -584,6 +588,11 @@ ifeq ($(PLATFORM),mingw32)
     TOOLS_BINEXT=.exe
   endif
 
+  ifeq ($(COMPILE_PLATFORM),cygwin)
+    TOOLS_BINEXT=.exe
+    TOOLS_CC=$(CC)
+  endif
+
   LIBS= -lws2_32 -lwinmm -lpsapi
   # clang 3.4 doesn't support this
   ifneq ("$(CC)", $(findstring "$(CC)", "clang" "clang++"))