diff --git a/clang/cmake/caches/Fuchsia.cmake b/clang/cmake/caches/Fuchsia.cmake
--- a/clang/cmake/caches/Fuchsia.cmake
+++ b/clang/cmake/caches/Fuchsia.cmake
@@ -17,6 +17,40 @@
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 
+# Passthrough stage1 flags to stage1.
+set(_FUCHSIA_BOOTSTRAP_PASSTHROUGH_STRINGS
+  ZLIB_INCLUDE_DIR
+  ZLIB_LIBRARY
+  zstd_DIR
+  LibXml2_ROOT
+  CURL_ROOT
+  OpenSSL_ROOT
+  CMAKE_SYSROOT
+  CMAKE_MODULE_LINKER_FLAGS
+  CMAKE_SHARED_LINKER_FLAGS
+  CMAKE_EXE_LINKER_FLAGS
+)
+
+set(_FUCHSIA_BOOTSTRAP_PASSTHROUGH_BOOL
+  LLVM_ENABLE_ZLIB
+  LLVM_ENABLE_ZSTD
+  LLVM_ENABLE_LIBXML2
+  LLVM_ENABLE_CURL
+  CMAKE_FIND_PACKAGE_PREFER_CONFIG
+)
+
+foreach(variableName ${_FUCHSIA_BOOTSTRAP_PASSTHROUGH_STRINGS})
+  if(DEFINED ${variableName})
+    set(BOOTSTRAP_${variableName} "${${variableName}}" CACHE STRING "")
+  endif()
+endforeach()
+
+foreach(variableName ${_FUCHSIA_BOOTSTRAP_PASSTHROUGH_BOOL})
+  if(DEFINED ${variableName})
+    set(BOOTSTRAP_${variableName} "${${variableName}}" CACHE BOOL "")
+  endif()
+endforeach()
+
 if(WIN32)
   set(LLVM_USE_CRT_RELEASE "MT" CACHE STRING "")
 endif()
@@ -105,12 +139,6 @@
   endif()
 endif()
 
-if(UNIX)
-  set(BOOTSTRAP_CMAKE_SHARED_LINKER_FLAGS "-ldl -lpthread" CACHE STRING "")
-  set(BOOTSTRAP_CMAKE_MODULE_LINKER_FLAGS "-ldl -lpthread" CACHE STRING "")
-  set(BOOTSTRAP_CMAKE_EXE_LINKER_FLAGS "-ldl -lpthread" CACHE STRING "")
-endif()
-
 set(BOOTSTRAP_LLVM_ENABLE_LLD ON CACHE BOOL "")
 set(BOOTSTRAP_LLVM_ENABLE_LTO ON CACHE BOOL "")
 
@@ -145,6 +173,8 @@
 set(CLANG_BOOTSTRAP_EXTRA_DEPS
   builtins
   runtimes
+  llvm-rc
+  llvm-mt
   CACHE STRING "")
 set(CLANG_BOOTSTRAP_CMAKE_ARGS
   ${EXTRA_ARGS}