[flang] Fix FIRSupport build race condition with HLFIRDialect

FIRSupports includes headers from HLFIRDialect that are generated at
compile time. Therefore it must wait until these headers have been
generated.

Fix flang bot failures:
https://lab.llvm.org/buildbot/#/builders/173/builds/10304

Author: jeanPerier

flang/lib/Optimizer/Support/CMakeLists.txt

@@ -8,6 +8,7 @@ add_flang_library(FIRSupport
 
   DEPENDS
   FIROpsIncGen
+  HLFIROpsIncGen
   MLIRIR
   ${dialect_libs}