Makefile: Allow building libquickjs as a shared library

Adapted from https://git.alpinelinux.org/aports/tree/community/quickjs/01-sharedlib.patch?id=27a8f649949c36bfc3e45854e08c48a8eb06e07c

Co-authored-by: Celeste <20312-Celeste@users.gitlab.alpinelinux.org>

Author: lanodan

Makefile

@@ -32,6 +32,8 @@ endif
 #CONFIG_WIN32=y
 # use link time optimization (smaller and faster executables but slower build)
 #CONFIG_LTO=y
+# also build libquickjs as a shared library
+#CONFIG_SHARED=y
 # consider warnings as errors (for development)
 #CONFIG_WERROR=y
 # force 32 bit build for some utilities
@@ -205,6 +207,10 @@ PROGS+=libquickjs.a
 ifdef CONFIG_LTO
 PROGS+=libquickjs.lto.a
 endif
+ifdef CONFIG_SHARED
+SO_VERSION=$(shell sed 's/-/./g' VERSION)
+PROGS+=libquickjs.so.$(SO_VERSION)
+endif
 
 # examples
 ifeq ($(CROSS_PREFIX),)
@@ -289,6 +295,11 @@ libquickjs.a: $(patsubst %.o, %.nolto.o, $(QJS_LIB_OBJS))
 	$(AR) rcs $@ $^
 endif # CONFIG_LTO
 
+ifdef CONFIG_SHARED
+libquickjs.so.$(SO_VERSION): $(patsubst %.o, %.pic.o, $(QJS_LIB_OBJS))
+	$(CC) -shared -Wl,-soname,$@ $(LDFLAGS) -o $@ $^
+endif # CONFIG_SHARED
+
 repl.c: $(QJSC) repl.js
 	$(QJSC) -c -o $@ -m repl.js
 
@@ -362,6 +373,10 @@ install: all
 	install -m644 libquickjs.a "$(DESTDIR)$(PREFIX)/lib/quickjs"
 ifdef CONFIG_LTO
 	install -m644 libquickjs.lto.a "$(DESTDIR)$(PREFIX)/lib/quickjs"
+endif
+ifdef CONFIG_SHARED
+	install -Dm755 libquickjs.so.$(SO_VERSION) "$(DESTDIR)$(PREFIX)/lib"
+	ln -s libquickjs.so.$(SO_VERSION) "$(DESTDIR)$(PREFIX)/lib/libquickjs.so"
 endif
 	mkdir -p "$(DESTDIR)$(PREFIX)/include/quickjs"
 	install -m644 quickjs.h quickjs-libc.h "$(DESTDIR)$(PREFIX)/include/quickjs"