dnsdist: Fix build readme - link, meson, mac brew

[karelbilek]

Short description

I fixed the readme for building dnsdist.

I didn't want to write Debian Linux instructions from scratch as I am not sure what all is needed there

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[rgacogne]

Looks good, thanks!

[coveralls]

Coverage Report for CI Build 27684184160

Coverage decreased (-16.8%) to 54.284%

Details

• Coverage decreased (-16.8%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 20012 coverage regressions across 192 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

20012 previously-covered lines in 192 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
pdns/recursordist/pdns_recursor.cc	1103	28.74%
pdns/tcpiohandler.cc	949	0.0%
pdns/auth-secondarycommunicator.cc	795	0.85%
pdns/rfc2136handler.cc	708	0.0%
pdns/packethandler.cc	686	29.17%
pdns/recursordist/lua-recursor4.cc	681	0.0%
modules/lmdbbackend/lmdbbackend.cc	661	46.07%
modules/bindbackend/bindbackend2.cc	599	12.46%
pdns/tcpreceiver.cc	588	14.11%
pdns/libssl.cc	558	0.0%

---

Coverage Stats

Relevant Lines:	114513
Covered Lines:	68098
Line Coverage:	59.47%
Relevant Branches:	57268
Covered Branches:	25152
Branch Coverage:	43.92%
Branches in Coverage %:	Yes
Coverage Strength:	2450081.89 hits per line

---

💛 - Coveralls