dev: use ruby_memcheck for a valgrind test task

Gemfile

@@ -1,3 +1,11 @@
 source "https://rubygems.org"
 
 gemspec
+
+gem("minitest", "~> 5.15")
+gem("rake-compiler", "~> 1.2.0")
+gem("rake-compiler-dock", "1.3.0")
+gem("rdoc", ">= 4.0", "< 7")
+gem("psych", "~> 4.0") # psych 5 doesn't build on some CI platforms yet
+
+gem("ruby_memcheck") if Gem::Platform.local.os == "linux"

rakelib/test.rake

@@ -1,7 +1,20 @@
 require "rake/testtask"
-
-Rake::TestTask.new(:test) do |t|
+test_config = lambda do |t|
   t.libs << "test"
   t.libs << "lib"
   t.test_files = FileList["test/**/test_*.rb"]
 end
+
+Rake::TestTask.new(:test, &test_config)
+
+begin
+  require "ruby_memcheck"
+
+  RubyMemcheck.config(binary_name: "sqlite3_native")
+
+  namespace :test do
+    RubyMemcheck::TestTask.new(:valgrind, &test_config)
+  end
+rescue LoadError => e
+  warn("NOTE: ruby_memcheck is not available in this environment: #{e}")
+end

sqlite3.gemspec

@@ -108,11 +108,5 @@ Gem::Specification.new do |s|
 
   s.add_dependency("mini_portile2", "~> 2.8.0")
 
-  s.add_development_dependency("minitest", "~> 5.15")
-  s.add_development_dependency("rake-compiler", "~> 1.2.0")
-  s.add_development_dependency("rake-compiler-dock", "1.3.0")
-  s.add_development_dependency("rdoc", ">= 4.0", "< 7")
-  s.add_development_dependency("psych", "~> 4.0") # psych 5 doesn't build on some CI platforms yet
-
   s.extensions << "ext/sqlite3/extconf.rb"
 end