build: fix linking against shared library

[mochaaP]

When building with shared libraries is enabled in the top-level project (e.g. aseprite here), laf still tries to find the vendored source.
This PR fixes the issue by checking whether a library is specified to use shared libs.

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I agree that my contributions are licensed under the MIT License.
You can find a copy of this license at https://opensource.org/licenses/MIT

Signed-off-by: Zephyr Lykos <self@mochaa.ws>

[dacap]

Hi @mochaaP, actually USE_SHARED_FREETYPE and USE_SHARED_HARFBUZZ are flags specified for Aseprite (not for laf). In this case, if we use Skia as a backend, I think we should check the args.gn file of the Skia compilation to check if we can link against the static version of these libraries or use the system ones (these flags are specified when Skia is built with skia_use_system_freetype2=false and skia_use_system_harfbuzz=false).

E.g. something like this is done to check if laf is being compiled with the same flags as Skia here.

[mochaaP]

Surely. I suppose we should also ensure that these two flags are in sync?

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by the way, it seems static linking is broken if the library is present on the host

$ ldd build/build_static/bin/aseprite
  linux-vdso.so.1 (0x00007fff72128000)
  libxcb.so.1 => /lib64/libxcb.so.1 (0x00007ff5658e2000)
  libGL.so.1 => /lib64/libGL.so.1 (0x00007ff56585b000)
  libfontconfig.so.1 => /lib64/libfontconfig.so.1 (0x00007ff56580c000)
  libSM.so.6 => /lib64/libSM.so.6 (0x00007ff565802000)
  libICE.so.6 => /lib64/libICE.so.6 (0x00007ff5657e4000)
  libX11.so.6 => /lib64/libX11.so.6 (0x00007ff56569d000)
  libXext.so.6 => /lib64/libXext.so.6 (0x00007ff565687000)
  libXcursor.so.1 => /lib64/libXcursor.so.1 (0x00007ff56567a000)
  libcrypto.so.3 => /lib64/libcrypto.so.3 (0x00007ff565200000)
  libacl.so.1 => /lib64/libacl.so.1 (0x00007ff565670000)
  libssl.so.3 => /lib64/libssl.so.3 (0x00007ff56515d000)
  libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007ff564e00000)
  libm.so.6 => /lib64/libm.so.6 (0x00007ff56507c000)
  libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007ff56564a000)
  libc.so.6 => /lib64/libc.so.6 (0x00007ff564a00000)
  /lib64/ld-linux-x86-64.so.2 (0x00007ff565935000)
  libXau.so.6 => /lib64/libXau.so.6 (0x00007ff565644000)
  libGLX.so.0 => /lib64/libGLX.so.0 (0x00007ff564dcd000)
  libGLdispatch.so.0 => /lib64/libGLdispatch.so.0 (0x00007ff564d15000)
  libfreetype.so.6 => /lib64/libfreetype.so.6 (0x00007ff564c45000)
  libxml2.so.2 => /lib64/libxml2.so.2 (0x00007ff56488c000)
  libuuid.so.1 => /lib64/libuuid.so.1 (0x00007ff565638000)
  libXrender.so.1 => /lib64/libXrender.so.1 (0x00007ff56562c000)
  libXfixes.so.3 => /lib64/libXfixes.so.3 (0x00007ff565074000)
  libz.so.1 => /lib64/libz.so.1 (0x00007ff56505a000)
  libattr.so.1 => /lib64/libattr.so.1 (0x00007ff564884000)
  libbz2.so.1 => /lib64/libbz2.so.1 (0x00007ff564870000)
  libpng16.so.16 => /lib64/libpng16.so.16 (0x00007ff564837000)
  libharfbuzz.so.0 => /lib64/libharfbuzz.so.0 (0x00007ff564739000)
  libbrotlidec.so.1 => /lib64/libbrotlidec.so.1 (0x00007ff56472c000)
  liblzma.so.5 => /lib64/liblzma.so.5 (0x00007ff5646f9000)
  libglib-2.0.so.0 => /lib64/libglib-2.0.so.0 (0x00007ff5645b0000)
  libgraphite2.so.3 => /lib64/libgraphite2.so.3 (0x00007ff56458f000)
  libbrotlicommon.so.1 => /lib64/libbrotlicommon.so.1 (0x00007ff56456c000)
  libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007ff5644d2000)