Update ROOT and Cling to LLVM20 #24820

Job	Run time
mac-beta ARM64	49m 4s
Windows 10 x86 Release	1h 14m 30s
mac15 ARM64 CMAKE_CXX_STANDARD=23	30m 3s
mac14 X64 CMAKE_CXX_STANDARD=20	1h 7m 14s
mac26 ARM64	39m 34s
Upload Event Payload	5s
Windows 10 x64 Release	1h 52m 36s
fedora43 CMAKE_CXX_STANDARD=23	1h 13m 0s
alma8	1h 16m 28s
alma9 CMAKE_BUILD_TYPE=Debug	2h 25m 24s
ubuntu2404 CMAKE_BUILD_TYPE=Debug	2h 30m 30s
fedora42 CMAKE_CXX_STANDARD=23	1h 17m 8s
alma10	1h 34m 31s
alma9 march_native CMAKE_BUILD_TYPE=RelWithDebInfo, CMAKE_CXX_FLAGS=-march=native, CMAKE_C_FLAGS=-march=native, builtin_zlib=ON, builtin_zstd=ON	1h 34m 14s
alma9 modules_off runtime_cxxmodules=Off	1h 4m 44s
debian125 CMAKE_CXX_STANDARD=20, dev=ON, CMAKE_CXX_FLAGS=-Wsuggest-override	1h 47m 48s
ubuntu22 imt=Off, CMAKE_BUILD_TYPE=Debug	2h 20m 27s
ubuntu2510 CMAKE_CXX_STANDARD=23	1h 14m 25s
debian13 dev=ON, CMAKE_CXX_FLAGS=-Wsuggest-override	1h 34m 56s
ubuntu2504 CMAKE_CXX_STANDARD=23	1h 27m 8s
rawhide Fedora pydebug CMAKE_CXX_STANDARD=23	1h 12m 22s
alma10 clang Ninja CMAKE_C_COMPILER=clang, CMAKE_CXX_COMPILER=clang++	1h 31m 32s
alma9 arm64 CMAKE_BUILD_TYPE=RelWithDebInfo, builtin_zlib=ON, builtin_zstd=ON	1h 27m 15s
	1d 7h 44m 58s

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