Dockerfile.gcc: add -j$(nproc) to kernel and module build steps

The kernel build and NVIDIA out-of-tree module build were running
single-threaded. Add -j$(nproc) to utilize all available cores,
matching the pattern already used by ZFS and rtw88 builds.

Signed-off-by: Mikhail Malyshev <mike.malyshev@gmail.com>

Author: rucoder

Dockerfile.gcc

@@ -103,11 +103,10 @@ RUN mkdir -p /tmp/kernel-modules/boot /tmp/kernel-modules/lib/modules
 RUN --mount=type=cache,target=/root/.cache/ccache,id=kernel-ccache-${TARGETARCH} \
     ccache -z \
     && echo "Building kernel for ${TARGETARCH} with ARCH=${ARCH} and CROSS_COMPILE=${CROSS_COMPILE}" \
-    && CC="${CROSS_COMPILE}gcc" \
-    && make \
+    && make -j$(nproc) \
         LOCALVERSION="-${LOCALVERSION}" \
         KERNEL_DEF_CONFIG=tegra_eveos_defconfig -C kernel \
-    && make \
+    && make -j$(nproc) \
         LOCALVERSION="-${LOCALVERSION}" \
         INSTALL_MOD_STRIP=1 \
         INSTALL_MOD_PATH=/tmp/kernel-modules install -C kernel \
@@ -118,8 +117,7 @@ WORKDIR /kernel-src
 RUN --mount=type=cache,target=/root/.cache/ccache,id=nvmodules-ccache-${TARGETARCH} \
     ccache -z \
     && echo "Building NVIDIA modules for ${TARGETARCH} with ARCH=${ARCH} and CROSS_COMPILE=${CROSS_COMPILE}" \
-    && CC="${CROSS_COMPILE}gcc" \
-    && make \
+    && make -j$(nproc) \
         CROSS_COMPILE="${CROSS_COMPILE}" \
         KERNEL_HEADERS="/kernel-src/kernel/kernel-jammy-src" modules \
     && CROSS_COMPILE_STRIP=$("${CROSS_COMPILE}strip" | awk '{print $NF}') \