Add LCG_105b

To run the testing, add a comment with:

Bot test PACKAGE[ PACKAGE2 ...]|all in TOOLCHAIN|all [(only|also) for ARCH-LABEL-COMPILER-BUILDTYPE] please!

later followed by

Bot repeat please!

To ensure patches required for existing LCG branches are not lost, please add the respective labels: alsoTargeting:LCG_102-patches, alsoTargeting:master, etc.

cmake/toolchain/heptools-105b.cmake

+#---List of externals----------------------------------------------
+set(LCG_PYTHON_VERSION 3)
+include(heptools-dev-base)
+
+#---Additional External packages------(Generators)-----------------
+include(heptools-dev-generators)
+
+LCG_external_package(ROOT 6.30.06)
+
+#---Apple MacOS special removals and overwrites--------------------
+include(heptools-macos)
+
+if(LCG_ARCH MATCHES "aarch64")
+  include(heptools-devARM)
+endif()
+