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 +17,34 @@
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 
+# Passthrough stage1 flags to stage1.
+set(_FUCHSIA_BOOTSTRAP_PASSTHROUGH
+  LLVM_ENABLE_ZLIB
+  ZLIB_INCLUDE_DIR
+  ZLIB_LIBRARY
+  LLVM_ENABLE_ZSTD
+  zstd_DIR
+  LLVM_ENABLE_LIBXML2
+  LibXml2_ROOT
+  LLVM_ENABLE_CURL
+  CURL_ROOT
+  OpenSSL_ROOT
+  CMAKE_FIND_PACKAGE_PREFER_CONFIG
+  CMAKE_SYSROOT
+  CMAKE_MODULE_LINKER_FLAGS
+  CMAKE_SHARED_LINKER_FLAGS
+  CMAKE_EXE_LINKER_FLAGS
+)
+
+foreach(variable ${_FUCHSIA_BOOTSTRAP_PASSTHROUGH})
+  get_property(is_value_set CACHE ${variable} PROPERTY VALUE SET)
+  if(${is_value_set})
+    get_property(value CACHE ${variable} PROPERTY VALUE)
+    get_property(type CACHE ${variable} PROPERTY TYPE)
+    set(BOOTSTRAP_${variable} "${value}" CACHE ${type} "")
+  endif()
+endforeach()
+
 if(WIN32)
   set(LLVM_USE_CRT_RELEASE "MT" CACHE STRING "")
 endif()