[add] modules_install target to Makefile to work with PetaLinux

Makefile

@@ -1,9 +1,14 @@
 HOST_ARCH       ?= $(shell uname -m | sed -e s/arm.*/arm/ -e s/aarch64.*/arm64/)
 ARCH            ?= $(shell uname -m | sed -e s/arm.*/arm/ -e s/aarch64.*/arm64/)
-KERNEL_SRC_DIR  ?= /lib/modules/$(shell uname -r)/build
 BUILD_DIR       ?= $(PWD)
 _BUILD_DIR      ?= $(shell readlink -f $(BUILD_DIR))
 
+ifdef KERNEL_SRC
+  KERNEL_SRC_DIR  := $(KERNEL_SRC)
+else
+  KERNEL_SRC_DIR  ?= /lib/modules/$(shell uname -r)/build
+endif
+
 ifeq ($(ARCH), arm)
  ifneq ($(HOST_ARCH), arm)
    CROSS_COMPILE  ?= arm-linux-gnueabihf-
@@ -25,6 +30,9 @@ all:
 
 	$(MAKE) -C $(KERNEL_SRC_DIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) M=$(_BUILD_DIR) src=$(PWD) modules
 
+modules_install:
+	$(MAKE) -C $(KERNEL_SRC_DIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) M=$(_BUILD_DIR) src=$(PWD) modules_install
+
 clean:
 	$(MAKE) -C $(KERNEL_SRC_DIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) M=$(_BUILD_DIR) src=$(PWD) clean