[wasm] bootstraptest, basictest: disable backquote literal tests

WASI doesn't support spawning a new process for now.

basictest/test.rb

@@ -1960,6 +1960,8 @@ module EvTest
 test_ok(i7 == nil)
 end
 
+# WASI doesn't support spawning a new process for now.
+unless /wasi/ =~ RUBY_PLATFORM
 test_check "system"
 test_ok(`echo foobar` == "foobar\n")
 test_ok(`./miniruby -e 'print "foobar"'` == 'foobar')
@@ -2010,6 +2012,7 @@ module EvTest
 
 File.unlink script_tmp or `/bin/rm -f "#{script_tmp}"`
 File.unlink "#{script_tmp}.bak" or `/bin/rm -f "#{script_tmp}.bak"`
+end # not /wasi/ =~ RUBY_PLATFORM
 
 test_check "const"
 TEST1 = 1

bootstraptest/runner.rb

@@ -271,6 +271,14 @@ def show_progress(message = '')
   end
 end
 
+def target_platform
+  if @ruby
+    `#{@ruby} --disable-gems -e 'print RUBY_PLATFORM'`
+  else
+    RUBY_PLATFORM
+  end
+end
+
 def show_limit(testsrc, opt = '', **argh)
   result = get_result_string(testsrc, opt, **argh)
   if @tty and @verbose

bootstraptest/test_literal.rb

@@ -65,8 +65,11 @@
 assert_equal 'Symbol',          ':"a#{1+2}c".class'
 
 # xstring
-assert_equal "foo\n",           %q(`echo foo`)
-assert_equal "foo\n",           %q(s = "foo"; `echo #{s}`)
+# WASI doesn't support spawning a new process for now.
+if /wasi/ !~ target_platform
+  assert_equal "foo\n",           %q(`echo foo`)
+  assert_equal "foo\n",           %q(s = "foo"; `echo #{s}`)
+end
 
 # regexp
 assert_equal '',                '//.source'