[MinGW] Use lib prefix for libraries

[mati865]

Summary

In MinGW world, UNIX like lib prefix is preferred for the libraries. This patch adjusts CMake files to do that.

[mati865]

Also adjusted llvm-config.

[mstorsjo]

What's the practical effect of this? I see that a number of libraries already have a lib prefix prepended, like libclang/liblldb - I presume this changes the name of the individual libs (for BUILD_SHARED_LIBS=TRUE configurations)?

[mati865]

I haven't tried BUILD_SHARED_LIBS=TRUE TBH.

Effects visible at first glance:

bin/LLVM.dll          -> bin/libLLVM.dll
bin/LTO.dll             -> bin/libLTO.dll
lib/liblibclang.a      -> lib/libclang.a
lib/liblibclang.dll.a  -> lib/libclang.dll.a
lib/libliblldb.dll.a    -> lib/liblldb.dll.a

I'll create 2 clean build directories and diff them for more precise info.

[mstorsjo]

This looks good to me! I can push it later.

[mati865]

-DLLVM_ENABLE_PROJECTS="clang;lldb" -DLLVM_BUILD_LLVM_DYLIB=1 with only this patch applied (< is before, > is after):

$ diff <(cd ../build && find ./ | sort) <(cd ../build2/ && find ./ | sort)
38a39,41
> ./bin/libLLVM.dll
> ./bin/libLTO.dll
> ./bin/libRemarks.dll
51d53
< ./bin/LLVM.dll
119d120
< ./bin/LTO.dll
123d123
< ./bin/Remarks.dll
1460a1461
> ./lib/libclang.dll.a
1500,1501c1501
< ./lib/liblibclang.dll.a
< ./lib/libliblldb.dll.a
---
> ./lib/liblldb.dll.a

-DLLVM_ENABLE_PROJECTS="clang;lldb" -DBUILD_SHARED_LIBS=1:
long diff

clang/tools/libclang/CMakeLists.txt

 if(NOT LLVM_ENABLE_PIC OR LIBCLANG_BUILD_STATIC)
   set(ENABLE_STATIC STATIC)
 endif()
 
 if (WIN32 AND ENABLE_SHARED AND ENABLE_STATIC)
   unset(ENABLE_STATIC)
 endif()
 
-if(WIN32)
+if(MSVC)
   set(output_name "libclang")
 else()
   set(output_name "clang")
 endif()
 
 # libclang requires headers which need _ALL_SOURCE to build on AIX
 if (UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
     remove_definitions("-D_XOPEN_SOURCE=700")
install(DIRECTORY
             "lib${LLVM_LIBDIR_SUFFIX}/python${PythonVersion}/site-packages")
 endforeach()
 if(NOT LLVM_ENABLE_IDE)
   add_custom_target(libclang-python-bindings)
   add_llvm_install_targets(install-libclang-python-bindings
                            COMPONENT
                              libclang-python-bindings)
 endif()
-

lldb/source/API/CMakeLists.txt

else()
     # Don't use an explicit export.  Instead, tell the linker to
     # export all symbols.
     MESSAGE("-- Symbols (liblldb): exporting all symbols from the lldb and lldb_private namespaces")
     add_llvm_symbol_exports(liblldb ${CMAKE_CURRENT_SOURCE_DIR}/liblldb-private.exports)
   endif()
   set_target_properties(liblldb_exports PROPERTIES FOLDER "lldb misc")
 endif()
 
-if ( CMAKE_SYSTEM_NAME MATCHES "Windows" )
+if (MSVC)
   # Only MSVC has the ABI compatibility problem and avoids using FindPythonLibs,
   # so only it needs to explicitly link against ${Python3_LIBRARIES}
-  if (MSVC AND LLDB_ENABLE_PYTHON)
+  if (LLDB_ENABLE_PYTHON)
     target_link_libraries(liblldb PRIVATE ${Python3_LIBRARIES})
   endif()
 else()
   set_target_properties(liblldb
     PROPERTIES
     OUTPUT_NAME lldb
   )
 endif()
 
 if (NOT LLDB_BUILT_STANDALONE)
   add_dependencies(liblldb clang-resource-headers)
 endif()
 
 if(LLDB_BUILD_FRAMEWORK)
   include(LLDBFramework)
 endif()

llvm/cmake/modules/AddLLVM.cmake

function(llvm_add_library name)
   if(ARG_MODULE)
     set_target_properties(${name} PROPERTIES
       PREFIX ""
       SUFFIX ${LLVM_PLUGIN_EXT}
       )
   endif()
 
   if(ARG_SHARED)
-    if(WIN32)
+    if(MSVC)
       set_target_properties(${name} PROPERTIES
         PREFIX ""
         )
     endif()
 
     # Set SOVERSION on shared libraries that lack explicit SONAME
     # specifier, on *nix systems that are not Darwin.
     if(UNIX AND NOT APPLE AND NOT ARG_SONAME)