[CMake] Fix typo in error message for LLD in bootstrap builds.

[xgupta]

LGTM, Thanks! And @fcambus If you want to continue contributing to the llvm-project, I would suggest you ask for commit access so you can directly commit typo fixes without opening revisions. Instructions are here -https://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access.

[fcambus]

@xgupta Yes, I of course have plans to continue contributing to LLVM. I will apply for commit access, thanks for the suggestion!

clang/CMakeLists.txt

if (CLANG_ENABLE_BOOTSTRAP)
 
   set(STAMP_DIR ${CMAKE_CURRENT_BINARY_DIR}/${NEXT_CLANG_STAGE}-stamps/)
   set(BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${NEXT_CLANG_STAGE}-bins/)
 
   if(BOOTSTRAP_LLVM_ENABLE_LLD)
     # adding lld to clang-bootstrap-deps without having it enabled in
     # LLVM_ENABLE_PROJECTS just generates a cryptic error message.
     if (NOT "lld" IN_LIST LLVM_ENABLE_PROJECTS)
-      message(FATAL_ERROR "LLD is enabled in the boostrap build, but lld is not in LLVM_ENABLE_PROJECTS")
+      message(FATAL_ERROR "LLD is enabled in the bootstrap build, but lld is not in LLVM_ENABLE_PROJECTS")
     endif()
     add_dependencies(clang-bootstrap-deps lld)
   endif()
 
   # If the next stage is LTO we need to depend on LTO and possibly lld or LLVMgold
   if(BOOTSTRAP_LLVM_ENABLE_LTO OR LLVM_ENABLE_LTO AND NOT LLVM_BUILD_INSTRUMENTED)
     if(APPLE)
       add_dependencies(clang-bootstrap-deps LTO)