AVRO-4113: [c++] Don't generate tests files if test are not requested (#3298)

* Don't generate tests files if test are not requested

* Added algorithm include (needed for std::find_if)

Author: pkubanek

lang/c++/CMakeLists.txt

@@ -170,6 +170,13 @@ if (AVRO_BUILD_EXECUTABLES)
 
     target_link_libraries (precompile avrocpp_s)
 
+    add_executable (avrogencpp impl/avrogencpp.cc)
+    target_link_libraries (avrogencpp avrocpp_s ${Boost_LIBRARIES})
+endif ()
+
+if (AVRO_BUILD_TESTS)
+    enable_testing()
+
     macro (gen file ns)
         add_custom_command (OUTPUT ${file}.hh
             COMMAND avrogencpp
@@ -201,13 +208,6 @@ if (AVRO_BUILD_EXECUTABLES)
     gen (big_union big_union)
     gen (union_redundant_types redundant_types)
 
-    add_executable (avrogencpp impl/avrogencpp.cc)
-    target_link_libraries (avrogencpp avrocpp_s ${Boost_LIBRARIES})
-endif ()
-
-if (AVRO_BUILD_TESTS)
-    enable_testing()
-
     macro (unittest name)
         add_executable (${name} test/${name}.cc)
         target_link_libraries (${name} avrocpp_s ${Boost_LIBRARIES} ${SNAPPY_LIBRARIES} ${ZLIB_LIBRARIES})

lang/c++/impl/avrogencpp.cc

@@ -16,6 +16,7 @@
  * limitations under the License.
  */
 
+#include <algorithm>
 #include <cctype>
 #ifndef _WIN32
 #include <ctime>