[AD] Patch for makefile issue when compiling MSVC with Cygwin

[Andrei Ellman <ae-a-alleg@xxxxxxxxxx>]

When trying to compile Allegro 4.2.1 for MSVC using Cygwin, I got the 
following error:

makefile.vc:282: *** target pattern contains no `%'.  Stop.

After some research, I came to the conclusion that a ':' in the target 
pattern  was causing the problem. I had been able to compile it 
previously, so came to the conclusion that when upgrading Cygwin (the 
first time I had done so in a year), the ability for target-patterns to 
contain ':' must have disappeared.

I had been able to build the MinGW build using Cygwin, so I looked at 
how makefile.mgw handled it. I noticed the line "WINDIR_S = $(shell 
cygpath -S)" which used Cygwin's 'cygpath' command to get a path in the 
cygwin format which does not use a colon (ie. /cygdrive/c/foo/ instead 
of C:/foo/). This was not present in makefile.vc

The attatched patch fixes the problem. It uses 'cygpath' to obtain the 
Windows directory, and the MSVCDIR directory (I'm not sure how to pass a 
makefile variable to a 'shell' call, so instead, I passed in the shell's 
MSVCDIR or MSVCDir variable depending on which was available). For some 
reason, the runner.exe utility cannot cope with tool-paths in the 
cygpath format, so I also made a change to how the absolute pathnames 
for the tools were calculated.

So far, this has only been tried with Cygwin. I'm not sure if the ':' 
problem is a cygwin thing, or if a solution needs to be thought up for 
MinGW as well.

Anyway, here's what I get witn make -v
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for i686-pc-cygwin

--- makefile.vc.old	2006-11-26 12:13:58.000000000 +0100
+++ makefile.vc	2006-12-19 06:35:13.852212800 +0100
@@ -103,6 +103,14 @@
 
 .PHONY: badwin badmsvc badspaces
 
+ifdef ALLEGRO_USE_CYGWIN
+
+WINDIR_S = $(shell cygpath -S)
+WINDIR_U = $(subst \,/,$(WINDIR_S))
+WINDIR_D = $(subst /,\,$(WINDIR_S))
+
+else
+
 ifeq ($(OS),Windows_NT)
    WINSYSDIR = $(SYSTEMROOT)
    ifeq ($(WINSYSDIR),)
@@ -125,13 +133,14 @@
 	@echo Your SYSTEMROOT or windir environment variable is not set!
 endif
 
+endif # ALLEGRO_USE_CYGWIN
+
+
 ifdef MSVCDIR
-   MSVCDIR_U = $(subst \,/,$(MSVCDIR))
-   MSVCDIR_D = $(subst /,\,$(MSVCDIR))
+   MSVCDIR_MSVCDIR = $(MSVCDIR)
 else
 ifdef MSVCDir
-   MSVCDIR_U = $(subst \,/,$(MSVCDir))
-   MSVCDIR_D = $(subst /,\,$(MSVCDir))
+   MSVCDIR_MSVCDIR = $(MSVCDir)
 else
 badmsvc:
 	@echo Your MSVCDIR environment variable is not set!
@@ -139,6 +148,26 @@
 endif
 endif
 
+ifdef ALLEGRO_USE_CYGWIN
+
+# Note: Using ':=' instead of '=' to improve performance of parsing makefile.
+# ?: Is there a more elegant way of setting MSVCDIR_S? MSVCDIR_S := $(shell cygpath $(MSVCDIR_MSVCDIR)) does not seem to work.
+ifdef MSVCDIR
+   MSVCDIR_S := $(shell cygpath $$MSVCDIR)
+else
+ifdef MSVCDir
+   MSVCDIR_S := $(shell cygpath $$MSVCDir)
+endif
+endif
+   
+   MSVCDIR_U = $(subst \,/,$(MSVCDIR_S))
+   MSVCDIR_D = $(subst /,\,$(MSVCDIR_S))   
+else
+   MSVCDIR_U = $(subst \,/,$(MSVCDIR_MSVCDIR))
+   MSVCDIR_D = $(subst /,\,$(MSVCDIR_MSVCDIR))
+endif  # ALLEGRO_USE_CYGWIN
+
+
 NULLSTRING :=
 SPACE := $(NULLSTRING) # special magic to get an isolated space character
 
@@ -160,13 +189,21 @@
 
 # -------- Work out the absolute pathnames for some MSVC tools to avoid confusion --------
 
+ifdef ALLEGRO_USE_CYGWIN
+   # The runner.exe tool does not like paths in the /cygdrive/ format.
+   MSVCDIR_TOOLSDIR_U = $(subst \,/,$(MSVCDIR_MSVCDIR))
+else
+   MSVCDIR_TOOLSDIR_U = $(MSVCDIR_U)
+endif
+
+
 ifdef COMPILER_ICL
    MSVC_CL = icl
 else
-   MSVC_CL = $(MSVCDIR_U)/bin/cl
+   MSVC_CL = $(MSVCDIR_TOOLSDIR_U)/bin/cl
 endif
-MSVC_LINK = $(MSVCDIR_U)/bin/link
-MSVC_LIB = $(MSVCDIR_U)/bin/link -lib
+MSVC_LINK = $(MSVCDIR_TOOLSDIR_U)/bin/link
+MSVC_LIB = $(MSVCDIR_TOOLSDIR_U)/bin/link -lib
 MSVC_RC = rc