scons: Reduce all Cygwin platform names to 'cygwin'.

platform.system in SCons on Cygwin includes the OS version number.
Windows XP - CYGWIN_NT-5.1
Windows Vista - CYGWIN_NT-6.0
Windows 7 - CYGWIN_NT-6.1

Reduce all Cygwin platform variants to just 'cygwin' so anything
downstream can simply use 'cygwin' instead of the different full
platform names.

common.py

@@ -15,6 +15,8 @@ import SCons.Script.SConscript
 # Defaults
 
 host_platform = _platform.system().lower()
+if host_platform.startswith('cygwin'):
+    host_platform = 'cygwin'
 
 # Search sys.argv[] for a "platform=foo" argument since we don't have
 # an 'env' variable at this point.
@@ -81,7 +83,7 @@ def AddOptions(opts):
 	opts.Add(EnumOption('machine', 'use machine-specific assembly code', default_machine,
 											 allowed_values=('generic', 'ppc', 'x86', 'x86_64')))
 	opts.Add(EnumOption('platform', 'target platform', host_platform,
-											 allowed_values=('linux', 'cell', 'windows', 'winddk', 'wince', 'darwin', 'embedded', 'cygwin_nt-5.1', 'cygwin_nt-6.1', 'sunos5', 'freebsd8')))
+											 allowed_values=('linux', 'cell', 'windows', 'winddk', 'wince', 'darwin', 'embedded', 'cygwin', 'sunos5', 'freebsd8')))
 	opts.Add('toolchain', 'compiler toolchain', default_toolchain)
 	opts.Add(BoolOption('gles', 'EXPERIMENTAL: enable OpenGL ES support', 'no'))
 	opts.Add(BoolOption('llvm', 'use LLVM', default_llvm))

scons/gallium.py

@@ -195,6 +195,8 @@ def generate(env):
     # Determine whether we are cross compiling; in particular, whether we need
     # to compile code generators with a different compiler as the target code.
     host_platform = _platform.system().lower()
+    if host_platform.startswith('cygwin'):
+        host_platform = 'cygwin'
     host_machine = os.environ.get('PROCESSOR_ARCHITEW6432', os.environ.get('PROCESSOR_ARCHITECTURE', _platform.machine()))
     host_machine = {
         'x86': 'x86',

src/gallium/winsys/sw/xlib/SConscript

@@ -4,7 +4,7 @@
 
 Import('*')
 
-if env['platform'] in ('cygwin_nt-5.1', 'cygwin_nt-6.1', 'linux'):
+if env['platform'] in ('cygwin', 'linux'):
 
     env = env.Clone()