[gn build] Add missing llvm-profgen dependency

Or else a clean build fails with missing Attributes.inc.

utils/gn/secondary/llvm/unittests/tools/llvm-profgen/BUILD.gn

@@ -1,6 +1,9 @@
 import("//llvm/utils/unittest/unittest.gni")
 
 unittest("LLVMProfgenTests") {
-  deps = [ "//llvm/lib/Testing/Support" ]
+  deps = [
+    "//llvm/include/llvm/IR:public_tablegen",
+    "//llvm/lib/Testing/Support",
+  ]
   sources = [ "ContextCompressionTest.cpp" ]
 }