perf tools: Fix arm64 libjvmti build by generating unistd_64.h

Since commit 22f7208 ("tools headers: Update the syscall table with
the kernel sources") the arm64 syscall header is generated at build
time. Later, commit bfb713e ("perf tools: Fix arm64 build by
generating unistd_64.h") added a dependency to libperf to guarantee that
this header was created before building libperf or perf itself.

However, libjvmti also requires this header but does not depend on
libperf, leading to build failures such as:

  In file included from /usr/include/sys/syscall.h:24,
                   from /usr/include/syscall.h:1,
                   from jvmti/jvmti_agent.c:36:
  tools/arch/arm64/include/uapi/asm/unistd.h:2:10: fatal error: asm/unistd_64.h: No such file or directory
      2 | #include <asm/unistd_64.h>

Fix this by ensuring that libperf is built before libjvmti, so that
unistd_64.h is always available.

Fixes: 22f7208 ("tools headers: Update the syscall table with the kernel sources")
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Vincent Minet <v.minet@criteo.com>
Link: https://lore.kernel.org/r/20250922053702.2688374-1-v.minet@criteo.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: vminet

tools/perf/Makefile.perf

@@ -941,7 +941,7 @@ $(OUTPUT)dlfilters/%.so: $(OUTPUT)dlfilters/%.o
 ifndef NO_JVMTI
 LIBJVMTI_IN := $(OUTPUT)jvmti/jvmti-in.o
 
-$(LIBJVMTI_IN): FORCE
+$(LIBJVMTI_IN): prepare FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti
 
 $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)