lkmc_many_files: create package to test a rootfs with many files

Automatically pick up packages from under packages/ into BR2_EXTERNAL.

Move many subdirectory READMEs into the toplevel and link to toplevel from those subreadmes instead.

packages/sample_package/Config.in

@@ -0,0 +1,4 @@
+config BR2_PACKAGE_SAMPLE_PACKAGE
+	bool "sample_package"
+	help
+		Sample Buildroot package.

packages/sample_package/Makefile

@@ -0,0 +1,16 @@
+.PHONY: all clean
+
+CFLAGS_EXTRA ?= -fopenmp -std=c99 -Wall -Werror -Wextra
+IN_EXT ?= .c
+LIBS :=
+OUT_EXT ?= .out
+
+OUTS := $(addsuffix $(OUT_EXT), $(basename $(wildcard *$(IN_EXT))))
+
+all: $(OUTS)
+
+%$(OUT_EXT): %$(IN_EXT)
+	$(CC) $(CFLAGS) $(CFLAGS_EXTRA) -o '$@' '$<' $(LIBS)
+
+clean:
+	rm -f *'$(OUT_EXT)'

packages/sample_package/external.desc

@@ -0,0 +1 @@
+name: SAMPLE_PACKAGE

packages/sample_package/external.mk

@@ -0,0 +1,22 @@
+################################################################################
+#
+# sample_package
+#
+################################################################################
+
+SAMPLE_PACKAGE_VERSION = 1.0
+SAMPLE_PACKAGE_SITE = $(BR2_EXTERNAL_SAMPLE_PACKAGE_PATH)
+SAMPLE_PACKAGE_SITE_METHOD = local
+
+define SAMPLE_PACKAGE_BUILD_CMDS
+	# D contains the source code of this package.
+	# TARGET_CONFIGURE_OPTS contains several common options such as CFLAGS and LDFLAGS.
+	$(MAKE) -C '$(@D)' $(TARGET_CONFIGURE_OPTS)
+endef
+
+define SAMPLE_PACKAGE_INSTALL_TARGET_CMDS
+  # Anything put inside TARGET_DIR will end up on the guest relative to the root directory.
+  $(INSTALL) -D -m 0755 $(@D)/*.out '$(TARGET_DIR)'
+endef
+
+$(eval $(generic-package))

packages/sample_package/sample_package.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+	puts("hello sample_package");
+	return EXIT_SUCCESS;
+}