Include the test pre.js script only for tests.

configure.ac

@@ -413,10 +413,12 @@ AC_CHECK_FUNCS([posix_memalign])
 
 AC_SUBST([LIBTOOL_EXTRA_FLAGS])
 
-dnl Executables extension
+TEST_LDFLAGS=''
 AS_IF([test "x$EMSCRIPTEN" != "x"],[
   EXEEXT=.js
+  TEST_LDFLAGS='--pre-js pre.js'
 ])
+AC_SUBST(TEST_LDFLAGS)
 
 dnl Libtool.
 

test/default/Makefile.am

@@ -127,6 +127,8 @@ AM_CPPFLAGS = \
 	-I$(top_builddir)/src/libsodium/include/sodium \
 	-I$(top_srcdir)/test/quirks
 
+AM_LDFLAGS = @TEST_LDFLAGS@
+
 TESTS_TARGETS = \
 	aead_chacha20poly1305 \
 	auth \