Add llvm-pdbutil in LLVM_TOOLCHAIN_TOOLS

One can argue that it qualifies as a toolchain tool rather than "internal llvm
tool". This will make it part of builds which set the
LLVM_INSTALL_TOOLCHAIN_ONLY cmake option, such as the Windows installer.

Fixes https://github.com/llvm/llvm-project/issues/53461

Differential revision: https://reviews.llvm.org/D118606

llvm/cmake/modules/AddLLVM.cmake

@@ -1217,6 +1217,7 @@ if(NOT LLVM_TOOLCHAIN_TOOLS)
     llvm-nm
     llvm-objcopy
     llvm-objdump
+    llvm-pdbutil
     llvm-rc
     llvm-readobj
     llvm-size