Merge pull request #62173 from mhjacobson/freebsd-recognize-amd64

build: recognize `amd64` in `CMAKE_SYSTEM_PROCESSOR`

Author: compnerd

CMakeLists.txt

@@ -116,7 +116,7 @@ endif()
 if(SWIFT_HOST_VARIANT_ARCH)
   set(SWIFT_HOST_VARIANT_ARCH_default "${SWIFT_HOST_VARIANT_ARCH}")
 else()
-  if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64")
+  if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64|amd64")
     set(SWIFT_HOST_VARIANT_ARCH_default "x86_64")
   elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|ARM64|arm64")
     if(SWIFT_HOST_VARIANT_SDK_default STREQUAL OSX)