boulder/data: Ensure split-machine-functions are disabled in bolt flags

split-machine-functions is an optional flag for PGO optimize builds that
uses the profile data to split hot/cold/unlikely .text sections.

Although disabled by default, BOLT does it's own version of splitting
hot/cold .text which split-machine-functions gets in the way of.

boulder/data/macros/arch/base.yaml

@@ -449,6 +449,8 @@ flags               :
             cxx       : "-fno-reorder-blocks-and-partition​"
             ld        : "-Wl,-q"
         llvm:
+            c         : "-fno-split-machine-functions"
+            cxx       : "-fno-split-machine-functions"
             ld        : "-Wl,-q"
 
     # Toggle -fcommon (OFF)