configure.ac: add automake conditional "LINUX"

Makefile.am

@@ -617,12 +617,16 @@ libsystem_a_SOURCES = \
 	src/system/UniqueFileDescriptor.hxx \
 	src/system/Open.cxx src/system/Open.hxx \
 	src/system/EventPipe.cxx src/system/EventPipe.hxx \
-	src/system/EventFD.cxx src/system/EventFD.hxx \
-	src/system/SignalFD.cxx src/system/SignalFD.hxx \
-	src/system/EpollFD.cxx src/system/EpollFD.hxx \
 	src/system/PeriodClock.hxx \
 	src/system/Clock.cxx src/system/Clock.hxx
 
+if LINUX
+libsystem_a_SOURCES += \
+	src/system/EventFD.cxx src/system/EventFD.hxx \
+	src/system/SignalFD.cxx src/system/SignalFD.hxx \
+	src/system/EpollFD.cxx src/system/EpollFD.hxx
+endif
+
 # Event loop library
 
 libevent_a_SOURCES = \

configure.ac

@@ -138,6 +138,7 @@ haiku*)
 	;;
 esac
 
+AM_CONDITIONAL([LINUX], [test x$host_is_linux = xyes])
 AM_CONDITIONAL([ANDROID], [test x$host_is_android = xyes])
 AM_CONDITIONAL([HAVE_WINDOWS], [test x$host_is_windows = xyes])
 

src/system/EpollFD.cxx

@@ -28,7 +28,6 @@
  */
 
 #include "config.h"
-#ifdef USE_EPOLL
 #include "EpollFD.hxx"
 #include "Error.hxx"
 
@@ -38,5 +37,3 @@ EpollFD::EpollFD()
 	if (!fd.IsDefined())
 		throw MakeErrno("epoll_create1() failed");
 }
-
-#endif /* USE_EPOLL */

src/system/EventFD.cxx

@@ -28,7 +28,6 @@
  */
 
 #include "config.h"
-#ifdef __linux__
 #include "EventFD.hxx"
 #include "system/Error.hxx"
 #include "util/Compiler.h"
@@ -60,5 +59,3 @@ EventFD::Write() noexcept
 	gcc_unused ssize_t nbytes =
 		fd.Write(&value, sizeof(value));
 }
-
-#endif /* USE_EVENTFD */

src/system/SignalFD.cxx

@@ -28,7 +28,6 @@
  */
 
 #include "config.h"
-#ifdef __linux__
 #include "SignalFD.hxx"
 #include "Error.hxx"
 
@@ -52,5 +51,3 @@ SignalFD::Read() noexcept
 		? info.ssi_signo
 		: -1;
 }
-
-#endif /* __linux__ */