[gn build] add llvm-profgen to gn build

Didn't notice it missing due to https://reviews.llvm.org/D89707#2705110

utils/gn/secondary/llvm/test/BUILD.gn

@@ -255,6 +255,7 @@ group("test") {
     "//llvm/tools/llvm-opt-report",
     "//llvm/tools/llvm-pdbutil",
     "//llvm/tools/llvm-profdata",
+    "//llvm/tools/llvm-profgen",
     "//llvm/tools/llvm-rc",
     "//llvm/tools/llvm-readobj:symlinks",
     "//llvm/tools/llvm-reduce",

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

@@ -0,0 +1,23 @@
+executable("llvm-profgen") {
+  deps = [
+    "//llvm/lib/DebugInfo/Symbolize",
+    "//llvm/lib/IR",
+    "//llvm/lib/MC",
+    "//llvm/lib/MC/MCDisassembler",
+    "//llvm/lib/Object",
+    "//llvm/lib/ProfileData",
+    "//llvm/lib/Support",
+    "//llvm/lib/Target:AllTargetsDescs",
+    "//llvm/lib/Target:AllTargetsDisassemblers",
+    "//llvm/lib/Target:AllTargetsInfos",
+    "//llvm/lib/Transforms/IPO",
+  ]
+  sources = [
+    "CSPreInliner.cpp",
+    "PerfReader.cpp",
+    "ProfileGenerator.cpp",
+    "ProfiledBinary.cpp",
+    "PseudoProbe.cpp",
+    "llvm-profgen.cpp",
+  ]
+}