Add firmware build script for OVMF UEFI

firmware/build_ovmf.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+# build_ovmf.sh — Build OVMF UEFI firmware (EDK2) with SMM + Secure Boot
+# ---------------------------------------------------------------------------
+# Run from inside the EDK2 source tree (build/edk2).
+# Produces a combined OVMF.fd (CODE+VARS) at:
+#   Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd
+#
+set -euo pipefail
+
+TOOLCHAIN="${TOOLCHAIN:-GCC5}"
+TARGET="${TARGET:-RELEASE}"
+ARCH="${ARCH:-X64}"
+EDK2_DIR="${EDK2_DIR:-$(pwd)}"
+
+[ -f OvmfPkg/build.sh ] || {
+    echo "ERROR: not in EDK2 tree (OvmfPkg/build.sh missing) in $EDK2_DIR" >&2
+    exit 1
+}
+
+echo "=== Building EDK2 BaseTools (C toolchain) ==="
+make -C BaseTools/Source/C -j"$(nproc)"
+
+echo "=== Initializing EDK2 environment ==="
+# shellcheck disable=SC1091
+source edksetup.sh
+
+echo "=== Building OVMF ($ARCH/$TARGET/$TOOLCHAIN, SMM + Secure Boot) ==="
+OvmfPkg/build.sh \
+    -a "$ARCH" \
+    -b "$TARGET" \
+    -t "$TOOLCHAIN" \
+    -D SMM_REQUIRE=TRUE \
+    -D SECURE_BOOT_ENABLE=TRUE
+
+OVMF_FD="Build/OvmfX64/${TARGET}_${TOOLCHAIN}/FV/OVMF.fd"
+if [ -f "$OVMF_FD" ]; then
+    echo "=== OVMF firmware ready: $OVMF_FD ($(du -h "$OVMF_FD" | cut -f1)) ==="
+else
+    echo "ERROR: OVMF.fd not found at $OVMF_FD" >&2
+    exit 1
+fi