docs/config-prereqs.txt, .circleci/config.yml: clarify the different …

…Homebrew locations are due to architecture, not age [networkupstools#2502]

Signed-off-by: Jim Klimov <[email protected]>

.circleci/config.yml

@@ -111,7 +111,7 @@ jobs:
       # uses of sem_init() and sem_destroy() in nut-scanner.c)
       # NOTE: CANBUILD_NIT_TESTS=yes to check if single-executor environments
       # do not have a problem with it.
-      # NOTE: Older Homebrew versions used CI_CCACHE_SYMLINKDIR="/usr/local/opt/ccache/libexec"
+      # NOTE: x86 Homebrew versions used CI_CCACHE_SYMLINKDIR="/usr/local/opt/ccache/libexec"
       - run:
           name: "ci_build"
           command: |-

docs/config-prereqs.txt

@@ -1341,7 +1341,9 @@ for compilers, and Homebrew community packaging for dependencies (including
 `bash` since the system one is too old for `ci_build.sh` script syntax).
 
 See `.travis.yml` and `.circleci/config.yml` for practical details of the
-setup.
+setup, and https://brew.sh if you want to install it on your MacOS system
+(note that its default packaged locations differ depending on architecture --
+see https://docs.brew.sh/Installation for more details).
 
 Currently known dependencies for basic build include:
 ----
@@ -1355,14 +1357,14 @@ Currently known dependencies for basic build include:
 
 Note that ccache is installed in a different location than expected by default
 in the `ci_build.sh` script, so if your system allows to add the symbolic link
-to `/opt/homebrew/opt/ccache/libexec` (earlier `/usr/local/opt/ccache/libexec`)
+to `/opt/homebrew/opt/ccache/libexec` (`/usr/local/opt/ccache/libexec` on x86)
 as `/usr/lib/ccache` -- please do so as the easiest way out.
 
 Alternatively, to prepare building sessions with `ci_build.sh` you can:
 ----
 :; export CI_CCACHE_SYMLINKDIR="/opt/homebrew/opt/ccache/libexec"
 
-### ...or for older builders:
+### ...or for x86 builders:
 #:; export CI_CCACHE_SYMLINKDIR="/usr/local/opt/ccache/libexec"
 ----