Make QEMU build under musl

QEMU and its glib dependency use a few very bespoke glibc extensions which
musl doesn't implement. This disables their use to make this build on both glibc and musl.

Test Plan: `bazel build --crosstool_top=//build/toolchain/musl-host-gcc:musl_host_cc_suite @qemu//:qemu-x86_64-softmmu` works

X-Origin-Diff: phab/D738
GitOrigin-RevId: 606f750be4259ca8fcc19f4c0cc0ddd54dff2090
diff --git a/third_party/qemu/patches/pregenerated_config_files.patch b/third_party/qemu/patches/pregenerated_config_files.patch
index fd5fe68..ced72f5 100644
--- a/third_party/qemu/patches/pregenerated_config_files.patch
+++ b/third_party/qemu/patches/pregenerated_config_files.patch
@@ -74,7 +74,7 @@
 +
 +#undef CONFIG_COCOA
 +
-+#define CONFIG_COROUTINE_BACKEND ucontext
++#define CONFIG_COROUTINE_BACKEND sigaltstack
 +
 +#define CONFIG_COROUTINE_POOL 0
 +
@@ -160,7 +160,7 @@
 +
 +#define CONFIG_MADVISE 1
 +
-+#define CONFIG_MALLOC_TRIM
++#undef CONFIG_MALLOC_TRIM
 +
 +#define CONFIG_MEMBARRIER 1
 +