libbinder: Remove hardcoded PAGE_SIZE usage in binderLibTest

Bug: 325083392
Test: atest binderLibTest
Change-Id: I19530353ee3455573a824d42c146b6e4340f2358
diff --git a/libs/binder/tests/binderLibTest.cpp b/libs/binder/tests/binderLibTest.cpp
index cb1a1ee..0ee96e7 100644
--- a/libs/binder/tests/binderLibTest.cpp
+++ b/libs/binder/tests/binderLibTest.cpp
@@ -70,7 +70,7 @@
 }
 
 static ::testing::AssertionResult IsPageAligned(void *buf) {
-    if (((unsigned long)buf & ((unsigned long)PAGE_SIZE - 1)) == 0)
+    if (((unsigned long)buf & ((unsigned long)getpagesize() - 1)) == 0)
         return ::testing::AssertionSuccess();
     else
         return ::testing::AssertionFailure() << buf << " is not page aligned";