make: also specify optimisation level for linking

With emscripten, LLVM is translated to JS during linking
and the optimisation level also has an effect here.
This was a regression from 9b1fc2e
and apart from performance also brings the total size of the distributed
files back down to ~7MiB from ~19MiB after the options were split.

Author: TheOneric

Makefile

@@ -4,7 +4,7 @@
 BASE_DIR:=$(dir $(realpath $(firstword $(MAKEFILE_LIST))))
 DIST_DIR:=$(BASE_DIR)dist/libraries
 
-export LDFLAGS = -s ENVIRONMENT=web,webview,worker -s NO_EXIT_RUNTIME=1
+export LDFLAGS = -O3 -s ENVIRONMENT=web,webview,worker -s NO_EXIT_RUNTIME=1
 export CFLAGS = -O3 -s USE_PTHREADS=0
 export CXXFLAGS = $(CFLAGS)
 export PKG_CONFIG_PATH = $(DIST_DIR)/lib/pkgconfig