scons: Revamp how to specify targets to build.

Use scons target and dependency system instead of ad-hoc options.

Now is simply a matter of naming what to build. For example:

  scons libgl-xlib

  scons libgl-gdi

  scons graw-progs

  scons llvmpipe

and so on. And there is also the possibility of scepcified subdirs, e.g.

  scons src/gallium/drivers

If nothing is specified then everything will be build.

There might be some rough corners over the next days. Please bare with me.

common.py

@@ -8,6 +8,8 @@ import subprocess
 import sys
 import platform as _platform
 
+import SCons.Script.SConscript
+
 
 #######################################################################
 # Defaults
@@ -20,6 +22,15 @@ _platform_map = {
 default_platform = sys.platform
 default_platform = _platform_map.get(default_platform, default_platform)
 
+# Search sys.argv[] for a "platform=foo" argument since we don't have
+# an 'env' variable at this point.
+if 'platform' in SCons.Script.ARGUMENTS:
+    selected_platform = SCons.Script.ARGUMENTS['platform']
+else:
+    selected_platform = default_platform
+
+cross_compiling = selected_platform != default_platform
+
 _machine_map = {
 	'x86': 'x86',
 	'i386': 'x86',
@@ -37,38 +48,26 @@ if 'PROCESSOR_ARCHITECTURE' in os.environ:
 else:
 	default_machine = _platform.machine()
 default_machine = _machine_map.get(default_machine, 'generic')
+default_toolchain = 'default'
+
+if selected_platform == 'windows' and cross_compiling:
+    default_machine = 'x86'
+    default_toolchain = 'crossmingw'
 
 
 # find default_llvm value
 if 'LLVM' in os.environ:
     default_llvm = 'yes'
 else:
-    # Search sys.argv[] for a "platform=foo" argument since we don't have
-    # an 'env' variable at this point.
-    platform = default_platform
-    pattern = re.compile("(platform=)(.*)")
-    for arg in sys.argv:
-        m = pattern.match(arg)
-        if m:
-            platform = m.group(2)
-
     default_llvm = 'no'
     try:
-        if platform != 'windows' and subprocess.call(['llvm-config', '--version'], stdout=subprocess.PIPE) == 0:
+        if selected_platform != 'windows' and \
+           subprocess.call(['llvm-config', '--version'], stdout=subprocess.PIPE) == 0:
             default_llvm = 'yes'
     except:
         pass
 
 
-# find default_dri value
-if default_platform in ('linux', 'freebsd'):
-	default_dri = 'yes'
-elif default_platform in ('winddk', 'windows', 'wince', 'darwin'):
-	default_dri = 'no'
-else:
-	default_dri = 'no'
-
-
 #######################################################################
 # Common options
 
@@ -88,8 +87,7 @@ def AddOptions(opts):
 											 allowed_values=('generic', 'ppc', 'x86', 'x86_64')))
 	opts.Add(EnumOption('platform', 'target platform', default_platform,
 											 allowed_values=('linux', 'cell', 'windows', 'winddk', 'wince', 'darwin', 'embedded', 'cygwin', 'sunos5', 'freebsd8')))
-	opts.Add('toolchain', 'compiler toolchain', 'default')
+	opts.Add('toolchain', 'compiler toolchain', default_toolchain)
 	opts.Add(BoolOption('llvm', 'use LLVM', default_llvm))
-	opts.Add(BoolOption('dri', 'build DRI drivers', default_dri))
 	opts.Add(BoolOption('debug', 'DEPRECATED: debug build', 'yes'))
 	opts.Add(BoolOption('profile', 'DEPRECATED: profile build', 'no'))