[phobos] win64 and visual studio path crap

[Brad Roberts]

I know this topic has come up in various forms, but no good resolution has yet been codified.  I 
need to reduce the amount of hand hacking done inside the auto-tester that's specific to visual 
studio paths and win64.  The local patches conflicted with a pull request that's also trying to do 
some cleanup in this area.  I just pulled that request and re-did my local changes, but I think the 
problem needs to be addressed.  The paths wander from version to version, including the directory 
structure inside the compiler main directory.  IMHO, the makefiles need to stop trying to set the 
paths an instead pull them from the environment.

What I've done with the auto-tester is:

1) set in the environment 4 variables:

     export VCDIR="C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC"
     export SDKDIR="C:\Program Files (x86)\Microsoft SDKs\Windows\v7.1A"
     export VCBIN_DIR="$VCDIR\bin\x86_amd64"
     export INCLUDE="$VCDIR\include"


2) apply a set of patches to druntime/win64.mak, phobos/win64.mak, phobos/etc/c/zlib/win64.mak that 
look basically like:

diff --git a/win64.mak b/win64.mak
index daee7f6..b381a34 100644
--- a/win64.mak
+++ b/win64.mak
@@ -2,14 +2,11 @@

  MODEL=64

-VCDIR=\Program Files (x86)\Microsoft Visual Studio 10.0\VC
-SDKDIR=\Program Files (x86)\Microsoft SDKs\Windows\v7.0A
-
  DMD=dmd

-CC="$(VCDIR)\bin\amd64\cl"
-LD="$(VCDIR)\bin\amd64\link"
-LIB="$(VCDIR)\bin\amd64\lib"
+CC="$(VCBIN_DIR)\cl"
+LD="$(VCBIN_DIR)\link"
+LIB="$(VCBIN_DIR)\lib"
  CP=cp

  DOCDIR=doc


A similar one to use the env rather than a hardcoded value in dmd/test/d_do_test.d.

I hate breaking changes, so any thoughts on how to make this suck less without breaking people 
building on win64?  Alternately, if you're among the probably relatively few people building on 
win64, would you object to this change?

Thoughts?

Thanks,
Brad