build: populate env vars using "env"

environmental variables cannot be populated to the tests if they are
performed as target using `cmake --build ... --target <target>`.
where the '<target>' is defined using `add_custom_target()`.

in order to populate the environmental variables down to the the COMMAND
specified by `add_custom_target()`, we need to launch the test using
`env`.

in this change, `cmake -E env` is used to launch the test command using
a more CMake native way without explicitly relying on yet another
external tool -- "env".

without this change, `Seastar_TEST_ENVIRONMENT` won't take effect when
running the tests.

Signed-off-by: Kefu Chai <[email protected]>

tests/unit/CMakeLists.txt

@@ -142,13 +142,13 @@ function (seastar_add_test name)
         OUTPUT_NAME ${name}_test)
 
     add_dependencies (unit_tests ${executable_target})
-    set (forwarded_args COMMAND ${executable_target} ${args})
+    set (forwarded_args COMMAND ${CMAKE_COMMAND} -E env "${Seastar_TEST_ENVIRONMENT}" $<TARGET_FILE:${executable_target}> ${args})
   else ()
     if (NOT (parsed_args_KIND STREQUAL "CUSTOM"))
       message (FATAL_ERROR "SOURCES are required for ${parsed_args_KIND} tests")
     endif ()
 
-    set (forwarded_args COMMAND ${parsed_args_RUN_ARGS})
+    set (forwarded_args COMMAND ${CMAKE_COMMAND} -E env "${Seastar_TEST_ENVIRONMENT}" ${parsed_args_RUN_ARGS})
   endif ()
 
   #
@@ -175,8 +175,7 @@ function (seastar_add_test name)
 
   set_tests_properties (Seastar.unit.${name}
     PROPERTIES
-      TIMEOUT ${Seastar_TEST_TIMEOUT}
-      ENVIRONMENT "${Seastar_TEST_ENVIRONMENT}")
+      TIMEOUT ${Seastar_TEST_TIMEOUT})
 endfunction ()
 
 #