morello-webkit: Set +nocherirevoke on installed JSC binary

MRS breaks the continuous arena implementation. Ideally the continuous
arena would be written to not rely on jemalloc-specific APIs, but that's
not happening any time soon, and it would be good to get the WebKit
tests passing reliably in Arm's Morello CI so we can catch any
regressions.

This still isn't quite right, (s)dallocx currently don't honour the
flags even when not quarantining, so MALLOCX_TCACHE_NONE will do
nothing, but presumably the result of that is at worst memory being
leaked (due to mallocx with MALLOCX_TCACHE_NONE never using it) or some
other part of JSC allocating that memory instead, so hopefully things
still work.

Author: jrtc27

pycheribuild/projects/cross/webkit.py

@@ -30,6 +30,7 @@
 
 from enum import Enum
 
+from .cheribsd import BuildFreeBSD
 from .crosscompileproject import CrossCompileCMakeProject, DefaultInstallDir, GitRepository
 from ..simple_project import BoolConfigOption
 
@@ -157,6 +158,22 @@ def setup(self):
             else:
                 self.add_cmake_options(ENABLE_JIT_ARM64_EMBED_POINTERS_AS_ALIGNED_LITERALS=self.tier2ptrliterals)
 
+    def install(self, **kwargs):
+        # XXX: Work around MRS breaking continuous arena (uses non-portable
+        # APIs to allocate from the arena, which MRS ignores).
+        if self.crosscompile_target.is_cheri_purecap():
+            if self.compiling_for_host():
+                elfctl_root = "/"
+            else:
+                freebsd_builddir = self.target_info.get_rootfs_project(t=BuildFreeBSD, caller=self).objdir
+                elfctl_root = freebsd_builddir / "tmp"
+            elfctl_cmd = elfctl_root / "usr/bin/elfctl"
+
+        super().install(**kwargs)
+
+        if self.crosscompile_target.is_cheri_purecap():
+            self.run_cmd([elfctl_cmd, "-e", "+nocherirevoke", self.install_dir / "bin/jsc"])
+
     def run_tests(self):
         if self.compiling_for_host():
             self.fatal("Running host tests not implemented")