Generate scons substitute info in top file

SConstruct

@@ -1,4 +1,5 @@
 import os
+import platform
 
 #version info of the library, we use 5 chars from the git hash
 revision = os.popen('git describe --abbrev=5 --dirty --always').read()[:-1]
@@ -78,7 +79,6 @@ if os.environ.has_key('CC'):
     env['CC'] = os.environ['CC']
 
 env.AddMethod(InstallPerm)
-Export('env', 'build_type', 'prefix', 'version_info', 'test_xml')
 
 env.Append(CFLAGS = ['-std=gnu99','-Wall', '-Wextra', '-Wundef', '-Wcast-qual','-Wshadow' ,'-Wcast-align','-pipe', '-ggdb', '-pthread'])
 env.Append(LINKFLAGS = ['-O2', '-pthread'])
@@ -103,6 +103,13 @@ if GetOption('coverage'):
     env.Append(CFLAGS = ['--coverage'])
     env.Append(LINKFLAGS = ['--coverage'])
 
+# Generate substitute dictionary
+subst_info = dict(('@' + key + '@', version_info[key]) for key in version_info)
+subst_info['@prefix'] = prefix
+subst_info['@build_host@'] = platform.node()
+
+Export('env', 'build_type', 'prefix', 'version_info', 'test_xml', 'subst_info')
+
 #put all .sconsign files in one place
 env.SConsignFile()