tcmode: disable pseudo for gcc/g++/cpp

The sourcery toolchain writes temporary files to /tmp, and includes the
username. If multiple users are doing builds with pseudo enabled, it'll try to
write to the other user's file, since both will use 'root', and the build will
fail as a result.

We don't want to wrap all the toolcahin binaries, as they don't all call the
tools which write these lockfiles, and objcopy has to be excluded, as it
modifies installed binaries when the packaging process splits out the debug
info. If that operation occurs outside of pseudo's knowledge, Bad Things will
happen.

JIRA: MEIP-393, SB-1905

Signed-off-by: Christopher Larson <kergoth@gmail.com>

conf/distro/include/tcmode-external-sourcery.inc

@@ -158,15 +158,24 @@ def populate_toolchain_links(d):
 
     bindir = d.getVar('STAGING_BINDIR_TOOLCHAIN', True)
     bb.utils.mkdirhier(bindir)
+    wrapped = ['gcc', 'g++', 'cpp']
     for f in files:
         base = os.path.basename(f)
         newpath = os.path.join(bindir, base)
-        try:
-            os.symlink(f, newpath)
-        except OSError as exc:
-            if exc.errno == errno.EEXIST:
-                break
-            bb.fatal("Unable to populate toolchain binary symlink for %s: %s" % (newpath, exc))
+        if not os.path.exists(newpath):
+            if any(base.endswith(w) for w in wrapped):
+                with open(newpath, 'w') as new:
+                    new.write('#!/bin/sh\n')
+                    new.write('export PSEUDO_UNLOAD=1\n')
+                    new.write('exec {0} "$@"\n'.format(f))
+                os.chmod(newpath, 0755)
+            else:
+                try:
+                    os.symlink(f, newpath)
+                except OSError as exc:
+                    if exc.errno == errno.EEXIST:
+                        break
+                    bb.fatal("Unable to populate toolchain binary symlink for %s: %s" % (newpath, exc))
 
     # Ensure that we have a ld.bfd available, now that KERNEL_LD uses it
     ld = d.expand('${TARGET_PREFIX}ld')