buildman: Always use the full path in CROSS_COMPILE

The feature to set the toolchain path does not seem to be needed. It
causes problems with venv (see [1]). Let's remove it.

Add some tests while we are here.

It does not look like any docs changes are needed for this.

[1] https://patchwork.ozlabs.org/project/uboot/patch/20240621131423.2363294-6-sjg@chromium.org/

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Andrejs Cainikovs <andrejs.cainikovs@toradex.com>
diff --git a/tools/buildman/builder.py b/tools/buildman/builder.py
index c4384f5..c794177 100644
--- a/tools/buildman/builder.py
+++ b/tools/buildman/builder.py
@@ -255,7 +255,7 @@
 
     def __init__(self, toolchains, base_dir, git_dir, num_threads, num_jobs,
                  gnu_make='make', checkout=True, show_unknown=True, step=1,
-                 no_subdirs=False, full_path=False, verbose_build=False,
+                 no_subdirs=False, verbose_build=False,
                  mrproper=False, fallback_mrproper=False,
                  per_board_out_dir=False, config_only=False,
                  squash_config_y=False, warnings_as_errors=False,
@@ -279,8 +279,6 @@
             step: 1 to process every commit, n to process every nth commit
             no_subdirs: Don't create subdirectories when building current
                 source for a single board
-            full_path: Return the full path in CROSS_COMPILE and don't set
-                PATH
             verbose_build: Run build with V=1 and don't use 'make -s'
             mrproper: Always run 'make mrproper' when configuring
             fallback_mrproper: Run 'make mrproper' and retry on build failure
@@ -337,7 +335,6 @@
         self._step = step
         self._error_lines = 0
         self.no_subdirs = no_subdirs
-        self.full_path = full_path
         self.verbose_build = verbose_build
         self.config_only = config_only
         self.squash_config_y = squash_config_y