Ports/qemu: Use the coarse monotonic clock for timing CPU ticks

While this loses quite a bit of accuracy (although to no apparent
decrease in emulation quality) , it helps avoiding the additional
overhead of the `clock_gettime` syscall (as `CLOCK_MONOTONIC_COARSE`
is forwarded using the mapped time page) and we don't have to do a
HPET timer read for each tick.

This results in a decrease of Serenity boot time from 1h16m down to
42m when running on Serenity.

Ports/qemu/patches/0001-Add-build-system-support-for-SerenityOS.patch

@@ -8,7 +8,7 @@ Subject: [PATCH] Add build system support for SerenityOS
  1 file changed, 6 insertions(+)
 
 diff --git a/configure b/configure
-index 7c08c18..3177605 100755
+index 7c08c18358becf49779c876b0f3d17329df053c6..3177605054876b387cd2b93463025ee3203991e7 100755
 --- a/configure
 +++ b/configure
 @@ -496,6 +496,8 @@ elif check_define __NetBSD__; then