Fix broken links

SYSTEMS.md

@@ -26,7 +26,7 @@ reframe -c benchmarks/examples/sombrero -r --performance-report --system archer2
 
 ARCHER2 allows [choosing the CPU frequency](https://docs.archer2.ac.uk/user-guide/energy/#controlling-cpu-frequency) during jobs by setting the environment variable `SLURM_CPU_FREQ_REQ` to specific values.
 In ReFrame v3 the list of environment variables set by the framework is held by the dictionary attribute called `env_vars`, and you can initialise it on the command line when running a benchmark with `-S`/`--setvar`.
-For more details, see Setting environment variables in [`README.md`](./README.md).
+For more details, see Setting environment variables in [usage](use.md).
 For example, to submit a benchmark using the lowest CPU frequency (1.5 GHz) you can use
 
 ```
@@ -38,7 +38,7 @@ reframe -c benchmarks/examples/sombrero -r --performance-report --system archer2
 ARCHER2 is a Cray system, and they
 [recommend using a cray optimised python version](https://docs.archer2.ac.uk/user-guide/python/).
 The HPE Cray Python distribution can be loaded using `module load cray-python`.
-This is necessary to pip install excalibur-tests following the instructions in [README.md](./README.md).
+This is necessary to pip install excalibur-tests following the instructions in [install](install.md).
 
 ### Spack install path
 

benchmarks/apps/README.md

@@ -1,3 +1,3 @@
 # Supported benchmarks
 
-This directory contains the benchmarks currently supported by the project. More can be added by opening a Pull Request following the guidance in [`CONTRIBUTING.md`](../../CONTRIBUTING.md).
+This directory contains the benchmarks currently supported by the project. More can be added by opening a Pull Request following the guidance in [contributing](../docs/contributing.md).

docs/use.md

@@ -77,7 +77,7 @@ to `threads`.
 
 ## Usage on unsupported systems
 
-The configuration provided in [`reframe_config.py`](./reframe_config.py) lets you run the
+The configuration provided in [`reframe_config.py`](https://github.com/ukri-excalibur/excalibur-tests/blob/main/benchmarks/reframe_config.py) lets you run the
 benchmarks on pre-configured HPC systems.  However you
 can use this framework on any system by choosing the "default" system with `--system
 default`, or by using your own ReFrame configuration.  You can use the "default" system to run