make doesn't handle += correctly for exported per-target variables

[Manoj Srivastava]

Hi,
            [Please retain the CC to address@hidden so
            that the Debian Bug Tracking system can record your input]

          This has been reported by a debian user.

        Consider this makefile:
----------------------------------------------------------------------
#!/usr/bin/make -f

var1 = foo
var2 = bar
var3 = baz

VAR1 = VAR1
VAR2 = VAR2
VAR3 = VAR3

export var1
export var2
export var3
export VAR1
export VAR2
export VAR3

rule: VAR1 = $(var1)
rule: VAR2 += $(var2)
VAR3 += $(var3)

rule:
        @echo "var1='$(var1)' VAR1='$(VAR1)'"
        @echo "var2='$(var2)' VAR2='$(VAR2)'"
        @echo "var3='$(var3)' VAR3='$(VAR3)'"
        @echo "exported: var1='$${var1}' VAR1='$${VAR1}'"
        @echo "exported: var2='$${var2}' VAR2='$${VAR2}'"
        @echo "exported: var3='$${var3}' VAR3='$${VAR3}'"
----------------------------------------------------------------------
address@hidden:~/brainfood/jmagick/jmagick-5.4.3-0$ make -f test
var1='foo' VAR1='foo'
var2='bar' VAR2='VAR2 bar'
var3='baz' VAR3='VAR3 baz'
exported: var1='foo' VAR1='foo'
exported: var2='bar' VAR2='VAR2'
exported: var3='baz' VAR3='VAR3 baz'
==

Note how the second 'exported:' line doesn't show VAR2='VAR2 bar' as expected.

        manoj
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Manoj Srivastava   <address@hidden>  <http://www.debian.org/%7Esrivasta/>
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