Building Cairo.jl for AWS Lambda

[samoconnor]

See #133

Amazon Linux on the Lambda sandbox meets some of Cairo.jl's dependancies with system libraries.
There is no way to install new system libraries (i.e. no root access and no yum).
freetype and fontconfig are installed as system libraries but the versions are too old for pango.

This PR allows Cairo.jl to use the system versions of libgobject, libffi, libpng and libpixman, while everything else is built form source.

The commits make one change at a time:

• Remove runtime = false for libraries that are required at runtime (see ldd output in Building Cairo.jl for AWS Lambda #133).
• remove gettext (nothing depends on it)
• Add harfbuzz (required by pango)
• Update libfontconfig version. (and don't try to build libfontconfig against expat).
• add option JULIA_BINDEPS_DISABLE_SYSTEM_PACKAGE_MANAGERS
• add option JULIA_BINDEPS_IGNORE_SYSTEM_FONT_LIBS
• split dependancies into two groups (otherwise no @checked_lib statements are generated in deps.jl).

The resulting deps.jl contains this:

@checked_lib _jl_libgobject "/usr/lib64/libgobject-2.0.so"
@checked_lib _jl_libpango "/var/task/julia/v0.4/Cairo/deps/usr/lib/libpango-1.0.so"
@checked_lib _jl_libpangocairo "/var/task/julia/v0.4/Cairo/deps/usr/lib/libpangocairo-1.0.so"
@checked_lib _jl_libcairo "/var/task/julia/v0.4/Cairo/deps/usr/lib/libcairo.so"

[tkelman]

is harfbuzz needed everywhere? will need to add package manager sources for it if so, and provide a windows binary source.

the validate hook should just check for required versions or symbols rather than paths and environment variables.

[lobingera]

@tkelman; i'm not an pango expert, but their web-page claims:

Pango is designed to be modular; the core Pango layout engine can be used with different font backends. There are three basic backends, with multiple options for rendering with each.

• Client side fonts using the FreeType and fontconfig libraries, using HarfBuzz for complex-text handling. Rendering can be with with Cairo or Xft libraries, or directly to an in-memory buffer with no additional libraries.
• Native fonts on Microsoft Windows using Uniscribe for complex-text handling. Rendering can be done via Cairo or directly using the native Win32 API.
• Native fonts on MacOS X using CoreText for complex-text handling, rendering via Cairo.

so there seems to be a propability to setup a native system without harfbuzz

[tkelman]

Not sure. We get all these binaries from winrpm, all the windows-specific BuildProcess lines can likely be deleted since I don't think they've been used in 2+ years. I turned on AppVeyor since it was easy and the package currently works on Windows, better to keep it that way automatically while tweaking BinDeps. The opensuse build service that winrpm downloads from has the cross-compiled libraries including harfbuzz, so that just gets downloaded and seems to work fine. May need to adjust the winrpm provides lines if harfbuzz is going to be added as a separate library_dependency is all.

[samoconnor]

the validate hook should just check for required versions or symbols rather than paths and environment variables.

But how would we know what version of fontconfig to check for?

If fontconfig version x is installed on my system already, then the pango that is installed by yum install pango will probably work fine with fontconfig version x. However, the pango version installed by Autoconf might require fontconfig version y. There's no way that all the interdependent versions can be kept in sync all the time across platforms and distributions.

In this case I need a way to say "BinDeps should ignore system libraries A and B".

[tkelman]

The library group functionality is supposed to be preventing that mixed-source scenario of trying to use some libraries from the system and some from source. If it's not doing so that sounds like it may be a BinDeps bug, or a misusage here.

[tkelman]

JULIA_BINDEPS_DISABLE_SYSTEM_PACKAGE_MANAGERS seems reasonable to me (though it's getting awfully long, maybe drop the SYSTEM part to shorten it up a bit?) but would be better-suited to implement in BinDeps rather than in every package that uses it.

[nalimilan]

Use HTTPS everywhere possible, or nowhere.

[giordano]

Probably also this one is not necessary after #292

[davidanthoff]

Yeah, I think this PR should be closed. If it is still needed it would need a thorough update, but most likely it is just no longer relevant.