On 486, though x264 is there, I get:

ERROR: libx264 not found

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.libera.chat.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.

I have no clue why..

And though I explicitely disable lto with configure flags it insists to build
with LTO.

Now I get tons of link errors:

/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mask24b'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `w05'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `b01'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `b80'
/usr/bin/ld: libavcodec/libavcodec.so: undefined reference to `pd_2'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `w04'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mask24h'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `bFC'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `b00'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `bF8'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mask24l'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `w20'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mask24r'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mul15_hi'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mmx_ff'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `b08'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mul16_mid'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mul15_mid'
/usr/bin/ld: libavcodec/libavcodec.so: undefined reference to `pd_1'
/usr/bin/ld: libpostproc/libpostproc.so: undefined reference to `deringThreshold'
/usr/bin/ld: libswscale/libswscale.so: undefined reference to `mask24g'
...

This is pentium4..

This is pretty annoying: enabling LTO leads to assembly errors:

libswscale/x86/swscale_template.c: In function ‘yuv2bgr24_X_ar_mmx’:
libswscale/x86/swscale_template.c:623:5: error: ‘asm’ operand has impossible constraints
  623 |     YSCALEYUV2PACKEDX_ACCURATE
      |     ^

Disabling LTO only half-disabled LTO (I still see -flto in places and
it results in "undefined references".

This package is basically broken.. (which makes things tricky, as too many
packages need it).

Disabling more assembly code might result in terrible performance..

ok, –disable-asm, at least things build then and packages can be installed again.
Don't blame me, if the performace is really bad..
(i686 and pentium4 work this way)

On i486 still issues around:

/gcc/i486-pc-linux-gnu/11.2.0/../../../libx264.so: undefined reference to `x264_cabac_renorm_shift'
/gcc/i486-pc-linux-gnu/11.2.0/../../../libx264.so: undefined reference to `x264_cabac_transition'
/gcc/i486-pc-linux-gnu/11.2.0/../../../libx264.so: undefined reference to `x264_decimate_table8'
/gcc/i486-pc-linux-gnu/11.2.0/../../../libx264.so: undefined reference to `x264_decimate_table4'
/gcc/i486-pc-linux-gnu/11.2.0/../../../libx264.so: undefined reference to `x264_cabac_range_lps'

gcc -Wl,-O1,–sort-common,–as-needed,-z,relro,-z,now -flto -Wl,–as-needed -Wl,-z,noexecstack -pthread -

in configure. And I disable LTO with –disable-lto?

Ok, happens also without LTO (and devtools makepkg.conf for i486 contains a 'lto'
per default, which might not be that smart).

Well, disabled X.264 on i486 for now.

fixed on i686 and pentium4, in stable and testing.

Now they build in a i486 chroot on 64-bit but not on a 486 VM:

ERROR: librsvg-2.0 not found using pkg-config

weird.

Maybe librsvg-og is missing a pkg-config file, or it is an older version.

So, if meson decides to have -Db_lto=auto everywhere, and if !lto in makepkg.conf is not
disabling it, then we will have a lot of issues on i486 with LTO.

LTO in i486 is disabled because the toolchain fails to build currently with LTO support
enabled.

pacman -Ql librsvg-og | grep pc
librsvg-og /usr/lib/pkgconfig/librsvg-2.0.pc

so, maybe this is a similar issue like with x.264, something broke fundamenaly
when probing for certain library properties?

/usr/bin/ld: warning: libcroco-0.6.so.3, needed by /usr/lib/gcc/i486-pc-linux-gnu/11
.2.0/../../../librsvg-2.so, not found (try using -rpath or -rpath-link)
/usr/bin/ld: /usr/lib/gcc/i486-pc-linux-gnu/11.2.0/../../../librsvg-2.so: undefined
reference to `cr_parser_set_sac_handler'
/usr/bin/ld: /usr/lib/gcc/i486-pc-linux-gnu/11.2.0/../../../librsvg-2.so: undefined reference to `cr_selector_ref'

This is libcroco, why this is not a dependency of librsvg?

So let's rebuild librsvg-og against libcroco..

Should have been a dependency long time ago, when librsvg was still the C library..