gitlab-ci, build: Add comments about Meson weak .pc relocatability support

This limitation was already documented on Windows but
not on other platforms affected yet. Let's just paste it.

.gitlab-ci.yml

@@ -343,6 +343,7 @@ deps-debian:
   variables:
     GIT_STRATEGY: none
     RELOCATABLE_OPTION: '-Drelocatable-bundle=yes'
+    #meson.build forces non-relocatable .pc. See: https://github.com/mesonbuild/meson/issues/14346
     PKGCONF_RELOCATABLE_OPTION: '-Dpkgconfig.relocatable=true'
   script:
     - !reference [deps-debian-nonreloc, script]
@@ -641,6 +642,7 @@ gimp-win:
   variables:
     ARCH: arm64
     ORKA_RUNNER: tahoe-1
+    #meson.build forces non-relocatable .pc. See: https://github.com/mesonbuild/meson/issues/14346
     PKGCONF_RELOCATABLE_OPTION: '-Dpkgconfig.relocatable=true'
   before_script:
     - export GIMP_PREFIX="$PWD/_install-$(uname -m)"

build/linux/snap/snapcraft.yaml

@@ -109,6 +109,7 @@ parts:
       - -Dprefix=/usr
       - -Dlibdir=lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR
       - -Drelocatable-bundle=yes
+      #meson.build forces non-relocatable .pc. See: https://github.com/mesonbuild/meson/issues/14346
       - -Dpkgconfig.relocatable=true
       - -Dgi-docgen=disabled
       - -Dwith-docs=false
@@ -136,6 +137,7 @@ parts:
       - -Dprefix=/usr
       - -Dlibdir=lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR
       - -Drelocatable-bundle=yes
+      #meson.build forces non-relocatable .pc. See: https://github.com/mesonbuild/meson/issues/14346
       - -Dpkgconfig.relocatable=true
       - -Dgi-docgen=disabled
       - -Ddocs=false
@@ -167,6 +169,7 @@ parts:
       - -Dprefix=/usr
       - -Dlibdir=lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR
       - -Drelocatable-bundle=yes
+      #meson.build forces non-relocatable .pc. See: https://github.com/mesonbuild/meson/issues/14346
       - -Dpkgconfig.relocatable=true
       - -Dgi-docgen=disabled
       - -Dcheck-update=no