Only run frameheader_cache_test.pass.cpp on x86_64.

Although there is nothing architecturally specific, the
ifdef chains are too complicated otherwise.

GitOrigin-RevId: 3758b858ef3b39b3081bf9a567ead8bc69c9a208
diff --git a/test/frameheadercache_test.pass.cpp b/test/frameheadercache_test.pass.cpp
index df0f926..9397e70 100644
--- a/test/frameheadercache_test.pass.cpp
+++ b/test/frameheadercache_test.pass.cpp
@@ -3,6 +3,11 @@
 #include "../src/config.h"
 
 // Only run this test under supported configurations.
+// The frame header cache should work fine for other architectures,
+// but the #ifdefs end up being even more complicated than this.
+
+#ifdef __x86_64__
+
 // This #if chain is ugly, but see the comments in AddressSpace.hpp for
 // the reasoning.
 
@@ -82,3 +87,6 @@
 #else
 int main() { return 0; }
 #endif
+#else
+int main() { return 0;}
+#endif