try_compile: Pass linker flags into test project (#14066)

Copy CMAKE_EXE_LINKER_FLAGS into the test project generated by
try_compile, just like we already copy CMAKE_<LANG>_FLAGS.

Add CMake Policy CMP0056 to activate this behavior in a compatible way,
but do not warn by default when the policy is not set since it will
affect all try_compile calls.

Extend the RunCMake.try_compile test with a case covering this behavior
for each policy setting.

1 files changed, 13 insertions, 0 deletions

diff --git a/Tests/RunCMake/try_compile/CMP0056-stderr.txt b/Tests/RunCMake/try_compile/CMP0056-stderr.txt
new file mode 100644
index 0000000..5c1f0e4
--- /dev/null
+++ b/Tests/RunCMake/try_compile/CMP0056-stderr.txt
@@ -0,0 +1,13 @@
+before try_compile with CMP0056 WARN-default
+after try_compile with CMP0056 WARN-default
+*
+CMake Warning \(dev\) at CMP0056.cmake:[0-9]+ \(try_compile\):
+  Policy CMP0056 is not set: Honor link flags in try_compile\(\) source-file
+  signature.  Run "cmake --help-policy CMP0056" for policy details.  Use the
+  cmake_policy command to set the policy and suppress this warning.
+
+  For compatibility with older versions of CMake, try_compile is not honoring
+  caller link flags \(e.g.  CMAKE_EXE_LINKER_FLAGS\) in the test project.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.$