Fix whitespace in CMakeLists.txt

- all spaces no tabs
- indent with 4 spaces everywhere
diff --git a/programs/x509/CMakeLists.txt b/programs/x509/CMakeLists.txt
index 4e39e45..39b8b5b 100644
--- a/programs/x509/CMakeLists.txt
+++ b/programs/x509/CMakeLists.txt
@@ -1,5 +1,5 @@
 set(libs
-     mbedtls
+    mbedtls
 )
 
 if(USE_PKCS11_HELPER_LIBRARY)