diff --git a/openmp/libomptarget/DeviceRTL/CMakeLists.txt b/openmp/libomptarget/DeviceRTL/CMakeLists.txt
--- a/openmp/libomptarget/DeviceRTL/CMakeLists.txt
+++ b/openmp/libomptarget/DeviceRTL/CMakeLists.txt
@@ -18,6 +18,12 @@
   return()
 endif()
 
+# Check to ensure the host system is a supported host architecture.
+if(NOT CMAKE_HOST_SYSTEM_PROCESSOR MATCHES "(x86_64|ppc64le|aarch64)")
+  libomptarget_say("Not building DeviceRTL: unknown host arch: ${CMAKE_HOST_SYSTEM_PROCESSOR}")
+  return()
+endif()
+
 if (LLVM_DIR)
   # Builds that use pre-installed LLVM have LLVM_DIR set.
   # A standalone or LLVM_ENABLE_RUNTIMES=openmp build takes this route