Add site_scons binaries and site_init files

site_scons/binaries.py

@@ -0,0 +1,42 @@
+# files.py
+#
+# Utilities for working with files and paths in SCons.
+#
+# Eryn Wells <eryn@erynwells.me>
+
+import os
+
+
+def which(program):
+    '''
+    Given a program name, search the system environment's $PATH for a binary of
+    that name. If one exists, return its name. If not, return None. This
+    function will also use the system environment's $PATHEXT to find binaries
+    with appropriate extensions (i.e., .exe on Windows).
+    '''
+    is_executable = lambda path: (    os.path.exists(path)
+                                  and os.access(path, os.X_OK))
+
+    path, name = os.path.split(program)
+    if path:
+        if is_executable(program):
+            return program
+    else:
+        pathext = [''] + os.environ.get('PATHEXT', '').split(os.pathsep)
+        for path in os.environ.get('PATH', '').split(os.pathsep):
+            exe = os.path.join(path, program)
+            for ext in pathext:
+                candidate = exe + ext
+                if is_executable(candidate):
+                    return candidate
+    return None
+
+
+def first(binaries):
+    '''
+    Given a list of binaries, return the first one found.
+    '''
+    for binary in binaries:
+        if which(binary):
+            return binary
+    return None