Fix Windows LLVM build for addition of LLVM_LINK_LLVM_DYLIB flag

fixes #21621, since this flag was enabled in #21498 the llvm tools have
been linking against the LLVM shared library, which means on windows the
dll has to be copied to build_depsbindir in order for llvm-config to run

deps/llvm.mk

@@ -553,8 +553,14 @@ endif
 $(build_prefix)/manifest/llvm: | $(llvm_python_workaround)
 
 ifeq ($(LLVM_USE_CMAKE),1)
+ifeq ($(OS), WINNT)
+LLVM_INSTALL = \
+ cd $1 && $$(CMAKE) -DCMAKE_INSTALL_PREFIX="$2$$(build_prefix)" -P cmake_install.cmake && \
+ cp $2$$(build_shlibdir)/LLVM.dll $2$$(build_depsbindir)
+else
 LLVM_INSTALL = \
  cd $1 && $$(CMAKE) -DCMAKE_INSTALL_PREFIX="$2$$(build_prefix)" -P cmake_install.cmake
+endif
 else
 LLVM_INSTALL = \
  $(call MAKE_INSTALL,$1,$2,$3 $$(LLVM_MFLAGS) PATH="$$(llvm_python_workaround):$$$$PATH" DestSharedLibDir="$2$$(build_shlibdir)")