bug#30431: 27.0.50; "Work even if libpng is install in /usr/local" causes build failure

[Michael Heerdegen]

Robert Cochran <robert+Emacs@cochranmail.com> writes:

> Build fails with an undefined symbol reference:
>
> CCLD     temacs
> /usr/bin/ld: image.o: undefined reference to symbol 
> 'png_set_sig_bytes@@PNG16_0'
> //usr/lib64/libpng16.so.16: error adding symbols: DSO missing from command 
> line
> collect2: error: ld returned 1 exit status
> make[1]: *** [Makefile:606: temacs] Error 1
> make[1]: Leaving directory '/home/Sora/Programming/emacs/src'
> make: *** [Makefile:418: src] Error 2
>
> OS is Fedora 27 amd64, libpng is libpng.1.6.31-1.fc27.x86_64

Same build error here on Debian testing.  Dropping the cited commit
doesn't seem to help, though.


Michael.