docs: adds info about nix builds

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Author: vincenzopalazzo

README.md

@@ -18,6 +18,8 @@ Requires `libsqlite-dev` and `libcurl4-gnutls-dev`, both compiled against `glibc
 ./gradlew packageLinuxX64
 ```
 
+If you are on a system with a different glibc, try to use nix and build phoenixd inside the shell that you can create with the command `nix-shell .nix/shell.nix`.
+
 ### Native MacOS x64
 ```shell
 ./gradlew packageMacOSX64
@@ -31,4 +33,4 @@ Requires `libsqlite-dev` and `libcurl4-gnutls-dev`, both compiled against `glibc
 ### JVM
 ```shell
 ./gradlew distZip
-```
+```