Merge bitcoin-core/secp256k1#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 bitcoin#1233.

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

Tree-SHA512: 8188018589a5bcf0179647a039cdafcce661dc103a70a5bb9e6b6f680b899332ba30b1e9ef5dad2a8c22c315d7794747e49d8cf2e391eebea21e3d8505ee334b

Author: real-or-random

.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()