Building tests is optional (#122)

It's better to base the test-building condition on a command-line option
instead of the presence of Catch2. Building the tests is not necessary
for normal usage of redsea anyway.

.github/workflows/build.yml

@@ -81,7 +81,7 @@ jobs:
     - name: Install dependencies (brew)
       run: brew install meson libsndfile liquid-dsp nlohmann-json catch2 perl gcovr
     - name: meson setup
-      run: meson setup -Dwerror=true -Db_sanitize=address,undefined -Db_lundef=false -Db_coverage=true build
+      run: meson setup -Dwerror=true -Db_sanitize=address,undefined -Db_lundef=false -Db_coverage=true build -Dbuild_tests=true
     - name: compile & install
       run: cd build && meson install
     - name: download test data

meson.build

@@ -121,9 +121,11 @@ executable(
 ### Unit tests ###
 ##################
 
-catch2 = dependency('catch2-with-main', required: false)
+build_tests = get_option('build_tests')
+
+if build_tests
+  catch2 = dependency('catch2-with-main', required: true)
 
-if catch2.found()
   unit_test_exe = executable(
     'redsea-test-unit',
     [

meson_options.txt

@@ -0,0 +1 @@
+option('build_tests', type: 'boolean', value: false, description: 'Build unit tests (requires Catch2)')