toolchain-scripts.bbclass: adjust toolchain_create_tree_env_script to better replicate (e)SDK

Specifically:
1. Place the environment setup file into $B and not into $TMPDIR,
so that the recipe using the class can itself better decide what to do with the file.

2. Use global, unified sysroots (provided through build-sysroots recipe)
and not recipe-specific ones, as this allows flexible on-the-fly management of what
libraries are available to build applications, without having to modify any
recipes, similar to eSDK 'extensible' part.

This also requires adjustment of the sstate sametune_samegsigs test, as meta-ide-support
becomes dependent on $MACHINE (unified sysroots have it in their paths)
and needs to be excluded from the test.

3. Add a few missing settings that have been added to SDK environment files.

4. Add a snippet to the environment setup file that also runs the relocation scripts.
In regular SDKs this is executed by the SDK installer, in direct SDK we can do it when
setting up the environment.

(From OE-Core rev: db5dfd78ae441201778b1175f4fb9a3eba994899)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/sstatetests.py

@@ -444,7 +444,7 @@ BB_SIGNATURE_HANDLER = "OEBasicHash"
             f = []
             for root, dirs, files in os.walk(d):
                 for name in files:
-                    if "meta-environment" in root or "cross-canadian" in root:
+                    if "meta-environment" in root or "cross-canadian" in root or 'meta-ide-support' in root:
                         continue
                     if "qemux86copy-" in root or "qemux86-" in root:
                         continue