Test without --jit-debug by default

and let RUBY_DEBUG=1 job test it.

We usually don't use --jit-debug and we should test no --jit-debug by
default.

.travis.yml

@@ -59,6 +59,10 @@ env:
   - &make-test-only
     script:
       - $SETARCH make -s test TESTOPTS="${TESTOPTS=$JOBS -q --tty=no}"
+      - |- # allow extra test-all if specified
+        if [ -n $TEST_ALL_TESTS ]; then
+          $SETARCH make -s test-all -o exts TESTOPTS="${TESTOPTS} ${TEST_ALL_OPTS}" TESTS="$TEST_ALL_TESTS" RUBYOPT="-w"
+        fi
 
   - &gcc-8
     compiler: gcc-8
@@ -122,15 +126,11 @@ env:
   - &x86_64-linux
     name: x86_64-linux
     <<: *gcc-8
-    env:
-      - TEST_MJIT_SYMBOLS=1 # detect exports missing for MJIT
 
   - &arm64-linux
     name: arm64-linux
     arch: arm64
     <<: *gcc-8
-    env:
-      - TEST_MJIT_SYMBOLS=1
 
   - &jemalloc
     name: --with-jemalloc
@@ -146,6 +146,8 @@ env:
     <<: *make-test-only
     env:
       - GEMS_FOR_TEST=
+      - TEST_MJIT_SYMBOLS=1
+      - TEST_ALL_TESTS=test/ruby/test_jit.rb
       - cppflags='-DRUBY_DEBUG -DVM_CHECK_MODE=1 -DTRANSIENT_HEAP_CHECK_MODE -DRGENGC_CHECK_MODE -DENC_DEBUG'
 
   - &VM_CHECK_MODE