do not install glslang when compiling shared library (#6023)

Author: nihui

CMakeLists.txt

@@ -811,7 +811,11 @@ if(NCNN_VULKAN)
             option(ENABLE_OPT "" OFF)
             option(ENABLE_PCH "" OFF)
             option(GLSLANG_TESTS "" OFF)
-            option(GLSLANG_ENABLE_INSTALL "" ON)
+            if(NCNN_SHARED_LIB)
+                option(GLSLANG_ENABLE_INSTALL "" OFF)
+            else()
+                option(GLSLANG_ENABLE_INSTALL "" ON)
+            endif()
             add_subdirectory(glslang)
             if(NCNN_SHARED_LIB)
                 if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT CMAKE_CXX_COMPILER_FRONTEND_VARIANT MATCHES "MSVC"))