[SV 61218] Ensure MAKEFLAGS is expanded even with -e

If -e was given we weren't expanding MAKEFLAGS before passing it
through the environment to jobs: we don't expand variables we
receive from the environment and when -e is given we set the
origin of MAKEFLAGS to "environment override".  Check for MAKEFLAGS
specifically, which seems like a hack but I don't have a better
idea offhand.

* src/main.c (main): Drive-by: use o_default for MAKEOVERRIDES.
* src/variable.c (target_environment): Always expand MAKEFLAGS
regardless of the origin type.
* tests/scripts/options/dash-e: Create a test.

tests/scripts/options/dash-e

@@ -1,8 +1,6 @@
 #                                                                    -*-perl-*-
 
-$description = "The following test creates a makefile to ...";
-
-$details = "";
+$description = "Test the -e (environment overrides) option";
 
 $ENV{GOOGLE} = 'boggle';
 
@@ -12,4 +10,15 @@ all:; @echo "$(GOOGLE)"
 !,
               '-e', "boggle\n");
 
+# Ensure variables set on the command line have the origin correct
+# See SV 61218
+
+run_make_test(q!
+$(info FOO [$(origin FOO)]: $(value FOO))
+all: ;
+recurse: ; @$(MAKE) -f #MAKEFILE#
+!,
+              '-e --no-print-directory FOO=1 recurse',
+              "FOO [command line]: 1\nFOO [command line]: 1\n#MAKE#[1]: 'all' is up to date.");
+
 1;