Overwrite symlinks for config files

In Makefile, we are trying to remove old symlinks first and then create a symlink.
do the same thing in meson too.

Also, the line of the exception handling for FileExistsError is meaningless
as the above line is taking care of it instead and we shouldn't ignore it if
os.remove and os.symlink doesn't work somehow.

Fixes fontconfig/fontconfig#275
12 jobs for issue/275 in 12 minutes and 47 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #7687156
meson android arm64 fedora

00:01:29

passed #7687154
gst-macos-10.15
meson macos

00:03:10

passed #7687451
meson-mingw-w64-build

00:06:04

manual #7687155
docker windows 1809 allowed to fail manual
meson msys2
passed #7687149
meson-shared-build

00:05:15

passed #7687150
meson-static-build

00:04:27

passed #7687152
docker windows 1809
meson vs2017 amd64

00:01:24

passed #7687153
docker windows 1809
meson vs2017 x86

00:01:26

passed #7687148
mingw-build

00:03:27

passed #7687146
shared-build

00:06:42

passed #7687147
static-build

00:06:18

failed #7687151
allowed to fail
meson-mingw-w64-build

00:05:06