feat(runtime): Use .hsc to get _SC_PAGE_SIZE

The numbers are different for different platforms so we now get the correct value

src/journal/src/Journal/Internal/Mmap.hs → src/journal/src/Journal/Internal/Mmap.hsc

@@ -28,6 +28,9 @@ foreign import ccall unsafe "stdlib.h posix_memalign"
 foreign import ccall unsafe "unistd.h sysconf"
   c_sysconf :: CInt -> IO CLong
 
+#include <unistd.h>
+_SC_PAGE_SIZE = #const _SC_PAGE_SIZE
+
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 mmap :: Maybe (Ptr a) -> Int -> MemoryProtection -> MemoryVisibility -> Maybe Fd
@@ -121,8 +124,6 @@ posixMemalign align size = do
 
 sysconfPageSize :: IO Int
 sysconfPageSize = fromIntegral <$> c_sysconf _SC_PAGE_SIZE
-  where
-    _SC_PAGE_SIZE = 30
 
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