[llvm] [LLVM][Cygwin] Fix llvm-config shared library names (PR #136599)

[via llvm-commits]

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@@ -64,7 +64,11 @@ set(LLVM_CFLAGS "${LLVM_C_STD_FLAG} ${LLVM_DEFINITIONS}")
 set(LLVM_CXXFLAGS "${CMAKE_CXX${CMAKE_CXX_STANDARD}_STANDARD_COMPILE_OPTION} ${LLVM_CXX_STDLIB_FLAG} ${COMPILE_FLAGS} ${LLVM_DEFINITIONS}")
 set(LLVM_BUILD_SYSTEM cmake)
 set(LLVM_HAS_RTTI ${LLVM_CONFIG_HAS_RTTI})
-set(LLVM_DYLIB_VERSION "${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX}")
+if(CYGWIN)
+  set(LLVM_DYLIB_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}${LLVM_VERSION_SUFFIX}")
+else()
+  set(LLVM_DYLIB_VERSION "${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX}")
+endif()
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jeremyd2019 wrote:

The question is which other targets?  UNIXy targets put major and minor in the filename of the shared library (libLLVM.so.20.1).  MinGW targets puts just the major (libLLVM-20.dll).  Neither appear in the import library name (which is admittedly a PE/COFF thing).

https://github.com/llvm/llvm-project/pull/136599