CMake: Fix x86 detection

The value of CMAKE_SYSTEM_PROCESSOR depends on what the host linux distro
decides to name their toolchain. All of `i386`, `i686`, `x86` are common
values for 32-bit x86, so check for all of them.

CMakeLists.txt

@@ -83,7 +83,7 @@ if (${CMAKE_SYSTEM_PROCESSOR} STREQUAL "aarch64")
   set(PRELOAD_LIBRARY_PAGE_SIZE 65536)
   set(VDSO_NAME "LINUX_2.6.39")
   set(VDSO_SYMBOLS "__kernel_clock_getres; __kernel_rt_sigreturn; __kernel_gettimeofday; __kernel_clock_gettime;")
-elseif(${CMAKE_SYSTEM_PROCESSOR} MATCHES x86|x86_64)
+elseif(${CMAKE_SYSTEM_PROCESSOR} MATCHES i386|i686|x86|x86_64)
   set(x86ish true)
   set(has_syscallbuf true)
   set(FLAGS_COMMON "${FLAGS_COMMON} -msse2 -D__MMX__ -D__SSE__ -D__SSE2__")