refactor: rework test_manylinux.py to handle musllinux

This avoid duplicating integration tests.
Tests that are generic are going in the Anylinux class.
Tests specific to manylinux are going in the Manylinux class.
Tests specific to musllinux are going in the Musllinux class.

Author: mayeut

tests/integration/internal_rpath/Makefile

@@ -1,5 +1,9 @@
+.PHONY: all clean
+
 all: lib-src/b/libb.so lib-src/a/liba.so
 
+clean:
+	-rm -f lib-src/b/libb.so lib-src/a/liba.so
 
 lib-src/b/libb.so: lib-src/b/b.c
 	gcc -fPIC -shared -o lib-src/b/libb.so lib-src/b/b.c

tests/integration/multiple_top_level/Makefile

@@ -1,9 +1,13 @@
+.PHONY: all clean
+
 all: lib-src/b/libb.so lib-src/a/liba.so
 
+clean:
+	-rm -f lib-src/b/libb.so lib-src/a/liba.so
 
 lib-src/b/libb.so: lib-src/b/b.c
 	gcc -fPIC -shared -o lib-src/b/libb.so lib-src/b/b.c
 
 
 lib-src/a/liba.so: lib-src/b/libb.so lib-src/a/a.c
-	gcc -fPIC -shared -o lib-src/a/liba.so -Ilib-src/b -Llib-src/b -lb lib-src/a/a.c
+	gcc -fPIC -shared -o lib-src/a/liba.so -Ilib-src/b lib-src/a/a.c -Llib-src/b -lb

tests/integration/nonpy_rpath/extensions/testcrypt.cpp

@@ -2,5 +2,9 @@
 #include <crypt.h>
 
 std::string crypt_something() {
-    return std::string(crypt("will error out", NULL));
+    char const* result = crypt("will error out", "\0");
+    if (result == NULL) {
+        return std::string("*");
+    }
+    return std::string(result);
 }