compile a static crengine library

[benoit-pierre]

There's only one user: libkoreader-cre.so, compiling a static library helps reduce code size and improve performance (I have not benchmarked it again, but FWIR, it was about 10% faster). Additionally, change the default symbol visibility to inlinehidden for further code reduction.

Size reduction (as reported by size -t libs/*cre* using the debug build, no LTO):

	Size (bss+data+code)
Before	3.8 MB
Static lib	3.6 MB
Static lib + inlinehidden visibility	3.3 MB

So a 463.1 kB reduction.

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This change is 

[benoit-pierre]

WTF: /usr/bin/ccache g++ -D-DALLOW_KERNING=1 -D-DCR3_PATCH=1 -D-DMATHML_SUPPORT=1 -D-DUSE_FONTCONFIG=0 -D-DUSE_FREETYPE=1 -D-DUSE_FRIBIDI=1 -D-DUSE_HARFBUZZ=1 -D-DUSE_LIBUNIBREAK=1 -D-DUSE_LIBWEBP=1 -D-DUSE_LUNASVG=1 -D-DUSE_NANOSVG=0 -D-DUSE_SRELL_REGEX=1 -D-DUSE_UTF8PROC=1 -D-DUSE_ZSTD=1 -DCHM_SUPPORT_ENABLED=1 -DCR3_ANTIWORD_PATCH=1 -DCR_EMULATE_GETTEXT -DDEBUG=1…

[benoit-pierre]

Does not work for some reason (double free pointer crash in the emulator). Some difference in the flags used to compile cre.cpp and the crengine library? Normally I would compile the release build with LTO, as it's a good way to detect those issue (the linker will warn if some types have different definitions), but I can't compile the release build. Not because of the usual luajit issue (-ffast-math = borked minilua), but some other issue in the bowels of MuPDF… It looks the MuPDF build generates a debug lib while a release one is expected? Anyway, I give up.

[NiLuJe]

I don't usually have troubles with LTO builds, FWIW, but it's been a while since I last tried ;).

I'll fire one up to see how it fares...

[benoit-pierre]

LTO is not the issue, a standard release build fails.

[benoit-pierre]

The release build issue is because of using if(DEFINED ENV{KODEBUG}) instead of if($ENV{KODEBUG}) in several thirdparty CMakeFileList.txt.

The release build with a static library does work for some reason.

Moving more compilation flags (pretty much all of them) out of thirdparty/kpvcrlib/CMakeLists.txt to Makefile.defs fix the problem with the debug build.

Will clean up and revisit later.

[benoit-pierre]

Take 2: includes #1677, #1678, and use a custom crsetup.h header to avoid having to move the flags around.

[benoit-pierre]

Ah, can't re-open after force pushing…