base/bitbake.conf: Filter contents of PATH to only allow whitelisted tools

We currently have a determinism problem in that the host tools present
in PATH can influence the build. In particular, the presence of pkg-config
on the build host can mask missing pkgconfig class dependencies.

This adds in a new HOSTTOOLS variable and then uses it to set up a directory
of symlinks to the whitelisted host tools. This directory is placed as PATH
instead of the usual /usr/bin:/bin and so on.

This should improve determinism of builds and avoid the issues which have
been particularly obvious since the introduction of recipe specific sysroots.

If users find there is a tool missing, they can extend HOSTTOOLS from a global
class or global conf file.

Right now the settings should be enough to build everything in OE-Core.

(From OE-Core rev: fa764a403da34bb0ca9fa3767a9e9dba8d685965)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/base.bbclass

@@ -119,6 +119,25 @@ def get_lic_checksum_file_list(d):
             bb.fatal(d.getVar('PN') + ": LIC_FILES_CHKSUM contains an invalid URL: " + url)
     return " ".join(filelist)
 
+def setup_hosttools_dir(dest, toolsvar, d, fatal=True):
+    tools = d.getVar(toolsvar).split()
+    origbbenv = d.getVar("BB_ORIGENV", False)
+    path = origbbenv.getVar("PATH")
+    bb.utils.mkdirhier(dest)
+    notfound = []
+    for tool in tools:
+        desttool = os.path.join(dest, tool)
+        if not os.path.exists(desttool):
+            srctool = bb.utils.which(path, tool)
+            if "ccache" in srctool:
+                srctool = bb.utils.which(path, tool, direction=1)
+            if srctool:
+                os.symlink(srctool, desttool)
+            else:
+                notfound.append(tool)
+    if notfound and fatal:
+        bb.fatal("These tools appear to be unavailable in PATH, please install them in order to proceed:\n%s" % " ".join(notfound))
+
 addtask fetch
 do_fetch[dirs] = "${DL_DIR}"
 do_fetch[file-checksums] = "${@bb.fetch.get_checksum_file_list(d)}"
@@ -219,6 +238,9 @@ python base_eventhandler() {
         pkgarch_mapping(e.data)
         oe.utils.features_backfill("DISTRO_FEATURES", e.data)
         oe.utils.features_backfill("MACHINE_FEATURES", e.data)
+        # Works with the line in layer.conf which changes PATH to point here
+        setup_hosttools_dir(d.expand('${TMPDIR}/hosttools'), 'HOSTTOOLS', d)
+        setup_hosttools_dir(d.expand('${TMPDIR}/hosttools'), 'HOSTTOOLS_NONFATAL', d, fatal=False)
 
     if isinstance(e, bb.event.BuildStarted):
         localdata = bb.data.createCopy(e.data)