fix(amd64): re-add signal support

[LouisBrunner]

Split from #126

Changes:

• Re-add the amd64 signals blocking during syscalls
• Clean up the arm64 syscall assembly and use __NR___pthread_sigmask as suggested for amd64

[github-actions]

Smart Diff (macos-14): Failure

Expected tolerance same but got mixed-better instead

===================================================================
--- .github/macos-14-expected.txt
+++ .github/test/filtered-results.txt
@@ -107,9 +107,8 @@
 memcheck/tests/strchr                    (stderr)
 memcheck/tests/supponlyobj               (stderr)
 memcheck/tests/test-plo-no               (stderr)
 memcheck/tests/test-plo-yes              (stderr)
-memcheck/tests/thread_alloca             (stderr)
 memcheck/tests/threadname                (stderr)
 memcheck/tests/threadname_xml            (stderr)
 memcheck/tests/trivialleak               (stderr)
 memcheck/tests/undef_malloc_args         (stderr)
@@ -362,9 +361,8 @@
 none/tests/bug234814                     (stderr)
 none/tests/darwin/access_extended        (stderr)
 none/tests/darwin/apple-main-arg         (stderr)
 none/tests/darwin/bug228343              (stdout)
-none/tests/darwin/bug228343              (stderr)
 none/tests/darwin/rlimit                 (stderr)
 none/tests/empty-exe                     (stderr)
 none/tests/faultstatus                   (stderr)
 none/tests/fdbaduse                      (stderr)
@@ -382,9 +380,8 @@
 none/tests/fdleak_fcntl_xml              (stderr)
 none/tests/fdleak_ipv4                   (stderr)
 none/tests/fdleak_ipv4_xml               (stderr)
 none/tests/fdleak_open                   (stderr)
-none/tests/fdleak_open_xml               (stderr)
 none/tests/fdleak_pipe                   (stderr)
 none/tests/fdleak_pipe_xml               (stderr)
 none/tests/fdleak_socketpair             (stderr)
 none/tests/fdleak_socketpair_xml         (stderr)
@@ -395,8 +392,9 @@
 none/tests/libvex_test                   (stderr)
 none/tests/libvexmultiarch_test          (stderr)
 none/tests/map_unmap                     (stdout)
 none/tests/map_unmap                     (stderr)
+none/tests/mmap_fcntl_bug                (stderr)
 none/tests/nocwd                         (stdout)
 none/tests/nocwd                         (stderr)
 none/tests/require-text-symbol-2         (stderr)
 none/tests/scripts/shell                 (stderr)