arm/hafnium: fix kernel tool linking

We need to be sure that the host linker flags are passed to the kernel
build, as otherwise it is possible that binaries are incorrectly linked.
For example:

HOSTCC scripts/extract-cert
ld: .../recipe-sysroot-native/usr/lib/pkgconfig/../../../usr/lib/libcrypto.so: undefined reference to `pthread_once@GLIBC_2.34'

Signed-off-by: Ross Burton <ross.burton@arm.com>

meta-arm/recipes-bsp/hafnium/hafnium/host-ld.patch

@@ -0,0 +1,21 @@
+We need to be sure that the host linker flags are passed to the kernel build,
+as otherwise it is possible that binaries are incorrectly linked. For example:
+
+HOSTCC scripts/extract-cert
+ld: .../recipe-sysroot-native/usr/lib/pkgconfig/../../../usr/lib/libcrypto.so: undefined reference to `pthread_once@GLIBC_2.34'
+
+Upstream-Status: Inappropriate
+Signed-off-by: Ross Burton <ross.burton@arm.com>
+
+diff --git a/build/linux/linux.gni b/build/linux/linux.gni
+index 65cc9df..19adbfb 100644
+--- a/build/linux/linux.gni
++++ b/build/linux/linux.gni
+@@ -69,6 +70,7 @@ template("linux_kernel") {
+     "GCC_TOOLCHAIN_DIR=" + rebase_path("//prebuilts/linux-x64/gcc/bin"),
+     "ARCH=arm64",
+     "CROSS_COMPILE=aarch64-linux-gnu-",
++    "HOSTLDFLAGS=" + getenv("BUILD_LDFLAGS"),
+ 
+     # Build out-of-tree in `target_out_dir`.
+     "O=" + rebase_path(target_out_dir),

meta-arm/recipes-bsp/hafnium/hafnium_2.5.bb

@@ -11,6 +11,7 @@ inherit deploy python3native pkgconfig
 
 SRC_URI = "gitsm://git.trustedfirmware.org/hafnium/hafnium.git;protocol=https;branch=master \
            file://hashbang.patch \
+           file://host-ld.patch \
            file://pkg-config-native.patch \
            file://native-dtc.patch"
 SRCREV = "3a149eb219467c0d9336467ea1fb9d3fb65da94b"