Merge #1290: cmake: Set ENVIRONMENT property for examples on Windows

175db31 ci: Drop no longer needed `PATH` variable update on Windows (Hennadii Stepanov)
116d2ab cmake: Set `ENVIRONMENT` property for examples on Windows (Hennadii Stepanov)
cef3739 cmake, refactor: Use helper function instead of interface library (Hennadii Stepanov)

Pull request description:

  This PR simplifies running examples on Windows, because the DLL must reside either in the same folder where the executable is or somewhere in PATH.

  It is an alternative to #1233.

ACKs for top commit:
  real-or-random:
    utACK 175db31

Tree-SHA512: 8188018589a5bcf0179647a039cdafcce661dc103a70a5bb9e6b6f680b899332ba30b1e9ef5dad2a8c22c315d7794747e49d8cf2e391eebea21e3d8505ee334b

.cirrus.yml

@@ -386,7 +386,6 @@ task:
     cpu: 4
     memory: 3840MB
   env:
-    PATH: '%CIRRUS_WORKING_DIR%\build\src\RelWithDebInfo;%PATH%'
     x64_NATIVE_TOOLS: '"C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Auxiliary\Build\vcvars64.bat"'
     # Ignore MSBuild warning MSB8029.
     # See: https://learn.microsoft.com/en-us/visualstudio/msbuild/errors/msb8029?view=vs-2022

examples/CMakeLists.txt

@@ -1,24 +1,30 @@
-add_library(example INTERFACE)
-target_include_directories(example INTERFACE
-  ${PROJECT_SOURCE_DIR}/include
-)
-target_link_libraries(example INTERFACE
-  secp256k1
-  $<$<PLATFORM_ID:Windows>:bcrypt>
-)
+function(add_example name)
+  set(target_name ${name}_example)
+  add_executable(${target_name} ${name}.c)
+  target_include_directories(${target_name} PRIVATE
+    ${PROJECT_SOURCE_DIR}/include
+  )
+  target_link_libraries(${target_name}
+    secp256k1
+    $<$<PLATFORM_ID:Windows>:bcrypt>
+  )
+  set(test_name ${name}_example)
+  add_test(NAME ${test_name} COMMAND ${target_name})
+  if(BUILD_SHARED_LIBS AND MSVC)
+    # The DLL must reside either in the same folder where the executable is
+    # or somewhere in PATH. Using the latter option.
+    set_tests_properties(${test_name} PROPERTIES
+      ENVIRONMENT "PATH=$<TARGET_FILE_DIR:secp256k1>;$ENV{PATH}"
+    )
+  endif()
+endfunction()
 
-add_executable(ecdsa_example ecdsa.c)
-target_link_libraries(ecdsa_example example)
-add_test(NAME ecdsa_example COMMAND ecdsa_example)
+add_example(ecdsa)
 
 if(SECP256K1_ENABLE_MODULE_ECDH)
-  add_executable(ecdh_example ecdh.c)
-  target_link_libraries(ecdh_example example)
-  add_test(NAME ecdh_example COMMAND ecdh_example)
+  add_example(ecdh)
 endif()
 
 if(SECP256K1_ENABLE_MODULE_SCHNORRSIG)
-  add_executable(schnorr_example schnorr.c)
-  target_link_libraries(schnorr_example example)
-  add_test(NAME schnorr_example COMMAND schnorr_example)
+  add_example(schnorr)
 endif()