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/luajit/luajit.mk

@@ -17,12 +17,6 @@ ifeq ($(BR2_PACKAGE_LUAJIT_COMPAT52),y)
 LUAJIT_XCFLAGS += -DLUAJIT_ENABLE_LUA52COMPAT
 endif
 
-ifeq ($(BR2_STATIC_LIBS),y)
-LUAJIT_BUILDMODE = static
-else
-LUAJIT_BUILDMODE = dynamic
-endif
-
 # The luajit build procedure requires the host compiler to have the
 # same bitness as the target compiler. Therefore, on a x86 build
 # machine, we can't build luajit for x86_64, which is checked in
@@ -50,7 +44,7 @@ define LUAJIT_BUILD_CMDS
 		HOST_CC="$(LUAJIT_HOST_CC)" \
 		HOST_CFLAGS="$(HOST_CFLAGS)" \
 		HOST_LDFLAGS="$(HOST_LDFLAGS)" \
-		BUILDMODE=$(LUAJIT_BUILDMODE) \
+		BUILDMODE=dynamic \
 		XCFLAGS=$(LUAJIT_XCFLAGS) \
 		-C $(@D) amalg
 endef