waf: add toolchain tool for cross-compiling

Tools/ardupilotwaf/toolchain.py

@@ -0,0 +1,37 @@
+"""
+WAF Tool to select the correct toolchain based on the target archtecture.
+
+This tool must be loaded before compiler tools. Use the environment variable
+TOOLCHAIN to define the toolchain prefix.
+
+Example::
+
+    def configure(cfg):
+        cfg.env.TOOLCHAIN = 'arm-linux-gnueabihf'
+        cfg.load('toolchain')
+        cfg.load('cxx_compiler')
+"""
+
+from waflib import Utils
+
+suffixes = dict(
+    CXX='g++',
+    CC='gcc',
+    AS='gcc',
+    AR='ar',
+    LD='g++',
+    GDB='gdb',
+    OBJCOPY='objcopy',
+)
+
+def configure(cfg):
+    if not cfg.env.TOOLCHAIN:
+        cfg.env.TOOLCHAIN = 'native'
+        prefix = ''
+    else:
+        cfg.env.TOOLCHAIN = Utils.to_list(cfg.env.TOOLCHAIN)[0]
+        cfg.msg('Using toolchain prefix', cfg.env.TOOLCHAIN)
+        prefix = cfg.env.TOOLCHAIN + '-'
+
+    for k in suffixes:
+        cfg.env.append_value(k, prefix + suffixes[k])

wscript

@@ -74,6 +74,7 @@ def configure(cfg):
         else:
             cfg.env.prepend_value(k, val)
 
+    cfg.load('toolchain')
     cfg.load('compiler_cxx compiler_c')
     cfg.load('clang_compilation_database')
     cfg.load('waf_unit_test')