Add an OSX prompt to manually configure icu4c. (#17069)

Documentation fix. 

1 files changed, 2 insertions, 0 deletions

diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md

index ac8a7039d1..76c3e790cd 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -86,6 +86,8 @@ poetry install --extras all
 This will install the runtime and developer dependencies for the project.  Be sure to check
 that the `poetry install` step completed cleanly.
 
+For OSX users, be sure to set `PKG_CONFIG_PATH` to support `icu4c`. Run `brew info icu4c` for more details.
+
 ## Running Synapse via poetry
 
 To start a local instance of Synapse in the locked poetry environment, create a config file: