Merge pull request #88 from skreuzer/bsd

Fix builds on BSD.
Fixes #89 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4954805..c88cd8f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,7 +49,7 @@
   set(PROCESSOR_IS_ARM TRUE)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^aarch64")
   set(PROCESSOR_IS_AARCH64 TRUE)
-elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64)|(AMD64)|(^i.86$)")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64)|(AMD64|amd64)|(^i.86$)")
   set(PROCESSOR_IS_X86 TRUE)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(powerpc|ppc)")
   set(PROCESSOR_IS_POWER TRUE)