Bump Buildroot to 2021.02-rc3 (#1260)

* Rebase patches to Buildroot 2021.02-rc3

* Update Buildroot to 2021.02-rc3

* Declare Kernel headers to be Linux version 5.10 (since they are, and new Buildroot knows about 5.10)

buildroot/package/coremark/Config.in

@@ -0,0 +1,8 @@
+config BR2_PACKAGE_COREMARK
+	bool "coremark"
+	help
+	  CoreMark is a benchmark that measures the performance of
+	  microcontrollers (MCUs) and central processing units (CPUs)
+	  used in embedded systems
+
+	  https://www.eembc.org/coremark/

buildroot/package/coremark/coremark.hash

@@ -0,0 +1,3 @@
+# Locally computed
+sha256  99c5a6d63af85a281b4e4d6ccb522c446653c435dfec9455ad73ef9e71f28bde  coremark-1.01.tar.gz
+sha256  d72094a3cb629dc7712ae09b7b777416903c6670930928b5530f2ddfb2296888  LICENSE.md

buildroot/package/coremark/coremark.mk

@@ -0,0 +1,21 @@
+################################################################################
+#
+# CoreMark
+#
+################################################################################
+
+COREMARK_VERSION = 1.01
+COREMARK_SITE = $(call github,eembc,coremark,v$(COREMARK_VERSION))
+COREMARK_LICENSE = Apache-2.0
+COREMARK_LICENSE_FILES = LICENSE.md
+
+define COREMARK_BUILD_CMDS
+	$(TARGET_MAKE_ENV) $(MAKE) CC="$(TARGET_CC)" -C $(@D) \
+		PORT_DIR=linux$(if $(BR2_ARCH_IS_64),64) EXE= link
+endef
+
+define COREMARK_INSTALL_TARGET_CMDS
+	$(INSTALL) -D $(@D)/coremark $(TARGET_DIR)/usr/bin/coremark
+endef
+
+$(eval $(generic-package))