virnuma: Actually build huge page code

One of previous commits (e6258a33) tried to build the huge page code
only on Linux since it's Linux centric indeed. But it failed miserably
as it used 'WITH_LINUX' which is an automake conditional not a gcc
one. In the sources we need to use __linux__.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/util/virnuma.c

@@ -512,8 +512,8 @@ virNumaGetDistances(int node ATTRIBUTE_UNUSED,
 #endif
 
 
-/* currently all the hugepage stuff below is linux only */
-#if WITH_LINUX
+/* currently all the huge page stuff below is linux only */
+#ifdef __linux__
 
 # define HUGEPAGES_NUMA_PREFIX "/sys/devices/system/node/"
 # define HUGEPAGES_SYSTEM_PREFIX "/sys/kernel/mm/hugepages/"
@@ -849,7 +849,7 @@ virNumaGetPages(int node,
 }
 
 
-#else /* #if WITH_LINUX */
+#else /* #ifdef __linux__ */
 int
 virNumaGetPageInfo(int node ATTRIBUTE_UNUSED,
                    unsigned int page_size ATTRIBUTE_UNUSED,
@@ -873,4 +873,4 @@ virNumaGetPages(int node ATTRIBUTE_UNUSED,
                    _("page info is not supported on this platform"));
     return -1;
 }
-#endif /* #if WITH_LINUX */
+#endif /* #ifdef __linux__ */