Auto merge of #12787 - msreckovic:patch-1, r=larsbergstrom

Update README.md with further openssl instructions

Sometimes building with openssl requires major intervention of pointing the include path to the local installation of openssl, when the brew link refuses to link.
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because it’s a documentation change

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README.md

@@ -34,6 +34,17 @@ brew install openssl
 brew link --force openssl
 ```
 
+If you get this error during the brew link step:
+```sh
+Warning: Refusing to link: openssl
+```
+followed by a compile error not being able to find one or more
+openssl/ include files, you may want to try:
+```sh
+export DEP_OPENSSL_INCLUDE=/usr/local/include
+./mach build ...
+```
+
 If you get this error:
 ``` sh
 "Couldn't find libavformat", do the following: