[Fuchsia] Add BOOTSTRAP_BOOTSTRAP flags for PGO (#150448)

clang/cmake/caches/Fuchsia.cmake

diff --git a/clang/cmake/caches/Fuchsia.cmake b/clang/cmake/caches/Fuchsia.cmake
index ee1d681..a3f86f6 100644
--- a/clang/cmake/caches/Fuchsia.cmake
+++ b/clang/cmake/caches/Fuchsia.cmake
@@ -76,6 +76,9 @@
     get_property(value CACHE ${variable} PROPERTY VALUE)
     get_property(type CACHE ${variable} PROPERTY TYPE)
     set(BOOTSTRAP_${variable} "${value}" CACHE ${type} "")
+    if(FUCHSIA_ENABLE_PGO)
+      set(BOOTSTRAP_BOOTSTRAP_${variable} "${value}" CACHE ${type} "")
+    endif()
   endif()
 endforeach()