Build bootloader for running Hafnium on QEMU under TF-A.

Bug: 132429380
Change-Id: I454904b9d83134fc33e55038a1b8bc3b5a52d5b1
diff --git a/BUILD.gn b/BUILD.gn
index f25e246..c215a5a 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -21,6 +21,7 @@
     "//src:hafnium(:android_aarch64_clang)",
     "//src:hafnium(:qemu_aarch64_clang)",
     "//src:hafnium(:rpi4_clang)",
+    "//src/arch/aarch64/qemuloader:bl(:qemu_aarch64_clang)",
   ]
 }