buildman: Add support for building with clang

Add a -O option which allows building with clang.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/buildman/README

@@ -1046,6 +1046,16 @@ value for 'altbootcmd', but lost one for ' altbootcmd'.
 
 The -U option uses the u-boot.env files which are produced by a build.
 
+
+Building with clang
+===================
+
+To build with clang (sandbox only), use the -O option to override the
+toolchain. For example:
+
+   buildman -O clang-7 --board sandbox
+
+
 Other options
 =============
 

tools/buildman/builderthread.py

@@ -229,6 +229,7 @@ class BuilderThread(threading.Thread):
                 config_args = ['%s_defconfig' % brd.target]
                 config_out = ''
                 args.extend(self.builder.toolchains.GetMakeArguments(brd))
+                args.extend(self.toolchain.MakeArgs())
 
                 # If we need to reconfigure, do that now
                 if do_config:

tools/buildman/cmdline.py

@@ -74,6 +74,8 @@ def ParseArgs():
     parser.add_option('-o', '--output-dir', type='string',
           dest='output_dir', default='..',
           help='Directory where all builds happen and buildman has its workspace (default is ../)')
+    parser.add_option('-O', '--override-toolchain', type='string',
+          help="Override host toochain to use for sandbox (e.g. 'clang-7')")
     parser.add_option('-Q', '--quick', action='store_true',
           default=False, help='Do a rough build, with limited warning resolution')
     parser.add_option('-p', '--full-path', action='store_true',

tools/buildman/control.py

@@ -141,7 +141,7 @@ def DoBuildman(options, args, toolchains=None, make_func=None, boards=None,
 
     no_toolchains = toolchains is None
     if no_toolchains:
-        toolchains = toolchain.Toolchains()
+        toolchains = toolchain.Toolchains(options.override_toolchain)
 
     if options.fetch_arch:
         if options.fetch_arch == 'list':

tools/buildman/toolchain.py

@@ -54,9 +54,11 @@ class Toolchain:
         arch: Architecture of toolchain as determined from the first
                 component of the filename. E.g. arm-linux-gcc becomes arm
         priority: Toolchain priority (0=highest, 20=lowest)
+        override_toolchain: Toolchain to use for sandbox, overriding the normal
+                one
     """
     def __init__(self, fname, test, verbose=False, priority=PRIORITY_CALC,
-                 arch=None):
+                 arch=None, override_toolchain=None):
         """Create a new toolchain object.
 
         Args:
@@ -68,6 +70,7 @@ class Toolchain:
         """
         self.gcc = fname
         self.path = os.path.dirname(fname)
+        self.override_toolchain = override_toolchain
 
         # Find the CROSS_COMPILE prefix to use for U-Boot. For example,
         # 'arm-linux-gnueabihf-gcc' turns into 'arm-linux-gnueabihf-'.
@@ -81,6 +84,8 @@ class Toolchain:
             self.arch = arch
         else:
             self.arch = self.cross[:pos] if pos != -1 else 'sandbox'
+        if self.arch == 'sandbox' and override_toolchain:
+            self.gcc = override_toolchain
 
         env = self.MakeEnvironment(False)
 
@@ -150,11 +155,18 @@ class Toolchain:
         Args:
             full_path: Return the full path in CROSS_COMPILE and don't set
                 PATH
+        Returns:
+            Dict containing the environemnt to use. This is based on the current
+            environment, with changes as needed to CROSS_COMPILE, PATH and
+            LC_ALL.
         """
         env = dict(os.environ)
         wrapper = self.GetWrapper()
 
-        if full_path:
+        if self.override_toolchain:
+            # We'll use MakeArgs() to provide this
+            pass
+        elif full_path:
             env['CROSS_COMPILE'] = wrapper + os.path.join(self.path, self.cross)
         else:
             env['CROSS_COMPILE'] = wrapper + self.cross
@@ -164,6 +176,22 @@ class Toolchain:
 
         return env
 
+    def MakeArgs(self):
+        """Create the 'make' arguments for a toolchain
+
+        This is only used when the toolchain is being overridden. Since the
+        U-Boot Makefile sets CC and HOSTCC explicitly we cannot rely on the
+        environment (and MakeEnvironment()) to override these values. This
+        function returns the arguments to accomplish this.
+
+        Returns:
+            List of arguments to pass to 'make'
+        """
+        if self.override_toolchain:
+            return ['HOSTCC=%s' % self.override_toolchain,
+                    'CC=%s' % self.override_toolchain]
+        return []
+
 
 class Toolchains:
     """Manage a list of toolchains for building U-Boot
@@ -180,10 +208,11 @@ class Toolchains:
         paths: List of paths to check for toolchains (may contain wildcards)
     """
 
-    def __init__(self):
+    def __init__(self, override_toolchain=None):
         self.toolchains = {}
         self.prefixes = {}
         self.paths = []
+        self.override_toolchain = override_toolchain
         self._make_flags = dict(bsettings.GetItems('make-flags'))
 
     def GetPathList(self, show_warning=True):
@@ -234,7 +263,8 @@ class Toolchains:
             priority: Priority to use for this toolchain
             arch: Toolchain architecture, or None if not known
         """
-        toolchain = Toolchain(fname, test, verbose, priority, arch)
+        toolchain = Toolchain(fname, test, verbose, priority, arch,
+                              self.override_toolchain)
         add_it = toolchain.ok
         if toolchain.arch in self.toolchains:
             add_it = (toolchain.priority <