Expect uname in $PATH

Fixes #87
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d1fda33..b7d0613 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,7 +32,7 @@
 
 # Package architecture
 IF ( NOT DEFINED PACKAGE_ARCHITECTURE )
- EXECUTE_PROCESS(COMMAND "/bin/uname" "-m" OUTPUT_VARIABLE UNAME_M)
+ EXECUTE_PROCESS(COMMAND "uname" "-m" OUTPUT_VARIABLE UNAME_M)
  # strip trailing newline
  STRING(REPLACE "\n" "" PACKAGE_ARCHITECTURE ${UNAME_M})
 ENDIF ( NOT DEFINED PACKAGE_ARCHITECTURE )