[gdb/build, clang] Fix ignored aligned attribute

PR build/34279 reports a build failure with clang.

This is a regression since commit 6c85ef111b0 ("[gdb] Use using instead of
typedef"), which did:
...
-typedef long __attribute__ ((__aligned__ (4))) compat_x32_clock_t;
+using compat_x32_clock_t = long __attribute__ ((__aligned__ (4)));
...

The problem is that clang ignores the attribute.

Fix this by reverting this part of the commit.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34279