disable hidraw (not supported on OpenBSD)

Index: Makefile.am
--- Makefile.am.orig
+++ Makefile.am
@@ -8,7 +8,7 @@ pkgconfigdir=$(libdir)/pkgconfig
 endif
 
 if OS_LINUX
-pkgconfig_DATA=pc/hidapi-hidraw.pc pc/hidapi-libusb.pc
+pkgconfig_DATA=pc/hidapi-libusb.pc
 else
 pkgconfig_DATA=pc/hidapi.pc
 endif
@@ -16,7 +16,7 @@ endif
 SUBDIRS=
 
 if OS_LINUX
-SUBDIRS += linux libusb
+SUBDIRS += libusb
 endif
 
 if OS_DARWIN