Remove Conan from MacOS build

[kevinbackhouse]

Conan on macOS is not working (see #1976, #1980). It's probably related to the switch to macOS-11 in GitHub Actions, but I have no idea how to fix it. On the 0.27-maintenance branch, we don't use Conan on macOS, so maybe it would be easier to do the same on main.

[codecov]

Codecov Report

Merging #1986 (e87e440) into main (c5101e0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1986   +/-   ##
=======================================
  Coverage   61.26%   61.26%           
=======================================
  Files          96       96           
  Lines       19105    19105           
  Branches     9756     9756           
=======================================
  Hits        11705    11705           
  Misses       5079     5079           
  Partials     2321     2321           

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[piponazo]

For me it looks fine to remove the usage of conan for Mac. Somehow, it seems that the Mac images used by Github Action has already all the conan dependencies installed by default (Except gtest that you are handling with the new changes):

Found ZLIB: /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/lib/libz.tbd (found version "1.2.11") 
-- Found CURL: /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/lib/libcurl.tbd (found version "7.64.1")  
-- Found EXPAT: /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/lib/libexpat.tbd (found version "2.2.8") 
-- Performing Test Iconv_IS_BUILT_IN
-- Performing Test Iconv_IS_BUILT_IN - Failed
-- Found Iconv: /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/lib/libiconv.tbd  
-- ICONV_INCLUDE_DIR : /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/include
-- ICONV_LIBRARIES : /Applications/Xcode_13.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk/usr/lib/libiconv.tbd

Green light from my side 👍

[kevinbackhouse]

@piponazo: Thanks! Yes, I think the Github Action's VMs have a lot of developer tools pre-installed. I copied that gtest installation code from the 0.27-maintenance branch. And before that, I copied it from somewhere else, but I don't remember where!