Allow kiwix-build to build shared libs linked statically with deps.

We need to be able to build libzim as shared lib while using all
other dependencies statically (to not have libxapian.so, ... to distribute)

This add a new platform (static=False) that make all dependencies being
build in a static platform.

kiwixbuild/platforms/native.py

@@ -1,5 +1,8 @@
 from .base import PlatformInfo
 
+from kiwixbuild.utils import pj
+from kiwixbuild._global import option
+
 
 class NativePlatformInfo(PlatformInfo):
     build = 'native'
@@ -14,3 +17,33 @@ class NativeStatic(NativePlatformInfo):
     name = 'native_static'
     static = True
     compatible_hosts = ['fedora', 'debian']
+
+class NativeMixed(NativePlatformInfo):
+    name = 'native_mixed'
+    static = False
+    compatible_hosts =  ['fedora', 'debian']
+
+    def add_targets(self, targetName, targets):
+        print(targetName)
+        if option('target') == targetName:
+            return super().add_targets(targetName, targets)
+        else:
+            static_platform = self.get_platform('native_static', targets)
+            return static_platform.add_targets(targetName, targets)
+
+    def get_fully_qualified_dep(self, dep):
+        if isinstance(dep, tuple):
+            return dep
+        if option('target') == dep:
+            return 'native_mixed', dep
+        return 'native_static', dep
+
+    def set_env(self, env):
+        super().set_env(env)
+        static_platform = self.get_platform('native_static')
+        static_buildEnv = static_platform.buildEnv
+        static_install_dir = static_buildEnv.install_dir
+        env['CPPFLAGS'] = " ".join(['-I'+pj(static_install_dir, 'include'), env['CPPFLAGS']])
+        env['PATH'] = ':'.join([pj(static_install_dir, 'bin')] + [env['PATH']])
+        pkgconfig_path = pj(static_install_dir, static_buildEnv.libprefix, 'pkgconfig')
+        env['PKG_CONFIG_PATH'] = ':'.join([env['PKG_CONFIG_PATH'], pkgconfig_path])