PPC/S390: Disable builtin remap on P/Z linux

There is currently a bug in docker where fstat may not
return the correct device id and as a result a check under
`OS::RemapPages, stat_buf.st_dev != enclosing_region.dev`
fails, details on the bug:
https://github.com/moby/moby/issues/43512

Platform specific page sizes are also defined for kMaxPageSize
to fix compilation errors.

Change-Id: I026609329aa6432eda4f1880a0f586c0c2162461
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3601211Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#80111}

src/base/platform/platform.h

@@ -311,7 +311,8 @@ class V8_BASE_EXPORT OS {
   // Whether the platform supports mapping a given address in another location
   // in the address space.
   V8_WARN_UNUSED_RESULT static constexpr bool IsRemapPageSupported() {
-#if defined(V8_OS_MACOS) || defined(V8_OS_LINUX)
+#if (defined(V8_OS_MACOS) || defined(V8_OS_LINUX)) && \
+    !(defined(V8_TARGET_ARCH_PPC64) || defined(V8_TARGET_ARCH_S390X))
     return true;
 #else
     return false;

test/unittests/base/platform/platform-unittest.cc

@@ -23,8 +23,17 @@ namespace v8 {
 namespace base {
 
 #ifdef V8_TARGET_OS_WIN
-// Alignemnt is constrained on Windows.
+// Alignment is constrained on Windows.
 constexpr size_t kMaxPageSize = 4096;
+#elif V8_HOST_ARCH_PPC64
+#if defined(_AIX)
+// gcc might complain about overalignment (bug):
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89357
+constexpr size_t kMaxPageSize = 4096;
+#else
+// Native PPC linux has large (64KB) physical pages.
+constexpr size_t kMaxPageSize = 65536;
+#endif
 #else
 constexpr size_t kMaxPageSize = 16384;
 #endif