Fix building for "Linux Process" in non-FHS environments

Makefile

@@ -29,8 +29,9 @@ dirs-y = src
 cc-option=$(shell if test -z "`$(1) $(2) -S -o /dev/null -xc /dev/null 2>&1`" \
     ; then echo "$(2)"; else echo "$(3)"; fi ;)
 
-CFLAGS := -I$(OUT) -Isrc -I$(OUT)board-generic/ -std=gnu11 -O2 -MD \
-    -Wall -Wold-style-definition $(call cc-option,$(CC),-Wtype-limits,) \
+CFLAGS := -iquote $(OUT) -iquote src -iquote $(OUT)board-generic/ \
+		-std=gnu11 -O2 -MD -Wall \
+		-Wold-style-definition $(call cc-option,$(CC),-Wtype-limits,) \
     -ffunction-sections -fdata-sections -fno-delete-null-pointer-checks
 CFLAGS += -flto=auto -fwhole-program -fno-use-linker-plugin -ggdb3
 

src/linux/gpio.c

@@ -10,7 +10,7 @@
 #include <string.h> // memset
 #include <sys/ioctl.h> // ioctl
 #include <unistd.h> // close
-#include </usr/include/linux/gpio.h> // GPIOHANDLE_REQUEST_OUTPUT
+#include <linux/gpio.h> // GPIOHANDLE_REQUEST_OUTPUT
 #include "command.h" // shutdown
 #include "gpio.h" // gpio_out_write
 #include "internal.h" // report_errno

src/linux/main.c

@@ -4,7 +4,7 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include </usr/include/sched.h> // sched_setscheduler sched_get_priority_max
+#include <sched.h> // sched_setscheduler sched_get_priority_max
 #include <stdio.h> // fprintf
 #include <string.h> // memset
 #include <unistd.h> // getopt