Cygwin: refactored & simplified some of the OS define logic

platforms/posix/cmake/px4_impl_os.cmake

@@ -171,12 +171,15 @@ function(px4_os_add_flags)
 		)
 
 	# This block sets added_definitions and added_cxx_flags.
+	set(added_definitions
+		-D__PX4_POSIX
+		-Dnoreturn_function=__attribute__\(\(noreturn\)\)
+		)
+
 	if(UNIX AND APPLE)
-		set(added_definitions
-			-D__PX4_POSIX
+		list(APPEND added_definitions
 			-D__PX4_DARWIN
 			-D__DF_DARWIN
-			-Dnoreturn_function=__attribute__\(\(noreturn\)\)
 			)
 
 		set(added_cxx_flags)
@@ -197,21 +200,17 @@ function(px4_os_add_flags)
 		endif()
 
 	elseif(CYGWIN)
-		set(added_definitions
-			-D__PX4_POSIX
+		list(APPEND added_definitions
 			-D__PX4_CYGWIN
 			-D_GNU_SOURCE
 			-D__USE_LINUX_IOCTL_DEFS
-			-Dnoreturn_function=__attribute__\(\(noreturn\)\)
 			-U __CUSTOM_FILE_IO__
 			)
 
 	else()
-		set(added_definitions
-			-D__PX4_POSIX
+		list(APPEND added_definitions
 			-D__PX4_LINUX
 			-D__DF_LINUX
-			-Dnoreturn_function=__attribute__\(\(noreturn\)\)
 			)
 
 		# Use -pthread For linux/g++.

src/lib/rc/dsm.cpp

@@ -52,11 +52,11 @@
 #include "common_rc.h"
 #include <drivers/drv_hrt.h>
 
-#if defined (__PX4_LINUX) || defined (__PX4_DARWIN) || defined(__PX4_CYGWIN) || defined(__PX4_QURT)
-#define dsm_udelay(arg) usleep(arg)
-#else
+#if defined(__PX4_NUTTX)
 #include <nuttx/arch.h>
 #define dsm_udelay(arg)    up_udelay(arg)
+#else
+#define dsm_udelay(arg) usleep(arg)
 #endif
 
 // #define DSM_DEBUG

src/platforms/px4_time.h

@@ -16,11 +16,6 @@ __EXPORT unsigned int sleep(unsigned int sec);
 
 __END_DECLS
 
-#elif defined(__PX4_LINUX) || defined(__PX4_NUTTX) || defined(__PX4_DARWIN) || defined(__PX4_CYGWIN)
-
-#define px4_clock_gettime clock_gettime
-#define px4_clock_settime clock_settime
-
 #elif defined(__PX4_QURT)
 
 #include <sys/timespec.h>
@@ -33,4 +28,10 @@ int px4_clock_settime(clockid_t clk_id, struct timespec *tp);
 __EXPORT unsigned int sleep(unsigned int sec);
 
 __END_DECLS
+
+#else
+
+#define px4_clock_gettime clock_gettime
+#define px4_clock_settime clock_settime
+
 #endif