Support building as a static library

Signed-off-by: Andreas Zwinkau <qznc@web.de>

Makefile

@@ -12,8 +12,10 @@ CC = gcc
 EMCC = emcc
 AFL_CC = afl-gcc
 AFL_CXX = afl-g++
+AR = ar
 
 RELEASE_TARGET := $(BUILD_DIR)/libolm.so.$(VERSION)
+STATIC_RELEASE_TARGET := $(BUILD_DIR)/libolm.a
 DEBUG_TARGET := $(BUILD_DIR)/libolm_debug.so.$(VERSION)
 JS_TARGET := javascript/olm.js
 
@@ -120,6 +122,12 @@ $(DEBUG_TARGET): $(DEBUG_OBJECTS)
             $(OUTPUT_OPTION) $(DEBUG_OBJECTS)
 	ln -sf libolm_debug.so.$(VERSION) $(BUILD_DIR)/libolm_debug.so.$(MAJOR)
 
+static: $(STATIC_RELEASE_TARGET)
+.PHONY: static
+
+$(STATIC_RELEASE_TARGET): $(RELEASE_OBJECTS)
+ $(AR) rcs $@ $^
+
 js: $(JS_TARGET)
 .PHONY: js
 

README.rst

@@ -46,6 +46,12 @@ To build the Xcode workspace for Objective-C bindings, run:
     pod install
     open OLMKit.xcworkspace
 
+To build olm as a static library (which still needs libstdc++ dynamically) run:
+
+.. code:: bash
+
+    make static
+
 Release process
 ---------------