meson: Robustify compiler detection logic

meson: Robustify compiler detection logic

meson would fail to detect compiler type in some rare care where
specific substring '-xt' is detected in compiler --version output and
it so happens that this string can be generated by clang --version if
clang is installed into a directory containing 'xt-' in its name. with
recipe specific sysroots, this is quite likely to happen in OE build
system as we are seeing the issue with newly proposed gnome-text-editor
recipe

https://lists.openembedded.org/g/openembedded-devel/topic/90150031#96301

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>