performance.md: recommend to build with the right profile (#7930)

* performance.md: recommend to build with the right profile

* doc: also update the paths

Author: sylvestre

docs/src/performance.md

@@ -23,21 +23,21 @@ This three-way comparison provides clear insights into:
 First, you will need to build the binary in release mode. Debug builds are significantly slower:
 
 ```bash
-cargo build --features unix --release
+cargo build --features unix --profile profiling
 ```
 
 ```bash
 # Three-way comparison benchmark
 hyperfine \
   --warmup 3 \
   "/usr/bin/ls -R ." \
-  "./target/release/coreutils.prev ls -R ." \
-  "./target/release/coreutils ls -R ."
+  "./target/profiling/coreutils.prev ls -R ." \
+  "./target/profiling/coreutils ls -R ."
 
 # can be simplified with:
 hyperfine \
   --warmup 3 \
-  -L ls /usr/bin/ls,"./target/release/coreutils.prev ls","./target/release/coreutils ls" \
+  -L ls /usr/bin/ls,"./target/profiling/coreutils.prev ls","./target/profiling/coreutils ls" \
   "{ls} -R ."
 ```