Add support for multiple variable overrides

Now we can do:

$ b config.cxx.coptions=-O3 config.cxx.coptions=-O0

Or even:

$ b config.cxx.coptions=-O3 config.cxx.coptions+=-g

1 files changed, 3 insertions, 3 deletions

diff --git a/old-tests/variable/override/test.sh b/old-tests/variable/override/test.sh
index baef1ca..94ed61f 100755
--- a/old-tests/variable/override/test.sh
+++ b/old-tests/variable/override/test.sh
@@ -55,9 +55,9 @@ function test ()
 
 fail foo=bar[]             # error: unexpected [ in variable assignment 'foo=bar[]'
 fail foo=[string]bar       # error: typed override of variable foo
-fail "!foo=bar" "!foo=BAR" # error: multiple global overrides of variable foo
-fail "foo=bar" "foo=BAR"   # error: multiple project overrides of variable foo
-fail "%foo=bar" "%foo=BAR" # error: multiple project overrides of variable foo
+#fail "!foo=bar" "!foo=BAR" # error: multiple global overrides of variable foo
+#fail "foo=bar" "foo=BAR"   # error: multiple project overrides of variable foo
+#fail "%foo=bar" "%foo=BAR" # error: multiple project overrides of variable foo
 
 test --buildfile simple foo=bar ./ ./ <<< "bar"  # Multiple bootstraps of the same project.