add readme for runtime and a make target (#414)

.gitignore

@@ -24,3 +24,5 @@ corelib
 
 cairo-*.tar
 /cairo2
+*.dylib
+*.so

Makefile

@@ -1,4 +1,4 @@
-.PHONY: usage build book build-dev build-native coverage check test bench bench-ci doc doc-open install clean install-scarb install-scarb-macos build-alexandria
+.PHONY: usage build book build-dev build-native coverage check test bench bench-ci doc doc-open install clean install-scarb install-scarb-macos build-alexandria runtime
 
 #
 # Environment detection.
@@ -127,3 +127,12 @@ install-scarb-macos:
 
 build-alexandria:
 	cd tests/alexandria; scarb build
+
+runtime:
+	cargo b --release -p cairo-native-runtime
+ifeq ($(UNAME), Linux)
+	cp target/release/libcairo_native_runtime.so .
+endif
+ifeq ($(UNAME), Darwin)
+	cp target/release/libcairo_native_runtime.dylib .
+endif

runtime/README.md

@@ -0,0 +1,14 @@
+## The cairo native runtime
+
+This runtime is used automatically when using JIT, but when using AOT, the library needs to be shipped and put in a path where it can be found by a linker.
+
+### Getting the library for use in AOT
+
+```bash
+git clone https://github.com/lambdaclass/cairo_native
+cd cairo_native
+make runtime
+ls libcairo_native_runtime.*
+
+# copy it where you need it, such as /usr/local/lib where it will be found by the linker
+```