CMake: Handle finding of OpenSSL headers correctly

In Coin when provisioning for Android, we download and configure
the OpenSSL package, but don't actually build it. This means that
find_package(OpenSSL) can find the headers, but not the library,
and thus the package is marked as not found.

Previously the openssl_headers feature used the result of finding
the OpenSSL package, which led to it being disabled in the above
described Android case.

Introduce 2 new find scripts FindWrapOpenSSL and
FindWrapOpenSSLHeaders. FindWrapOpenSSLHeaders wraps FindOpenSSL,
and checks if the headers were found, regardless of the OpenSSL_FOUND
value, which can be used for implementing the openssl_headers feature.

FindWrapOpenSSL uses FindWrapOpenSSLHeaders, and simply wraps the
OpenSSL target if available.

The find scripts also have to set CMAKE_FIND_ROOT_PATH for Android.
Otherwise when someone passes in an OPENSSL_ROOT_DIR, its value will
always be prepended to the Android sysroot, causing the package not
to be found.

Adjust the mapping in helper.py to use the targets created by these
find scripts. This also replaces the openssl/nolink target.

Adjust the projects and tests to use the new target names.

Adjust the compile tests for dtls and oscp to use the
WrapOpenSSLHeaders target, so that the features can be enabled even
if the library is dlopen-ed (like on Android).

Task-number: QTBUG-83371
Change-Id: I738600e5aafef47a57e1db070be40116ca8ab995
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

2 files changed, 55 insertions, 0 deletions

diff --git a/cmake/FindWrapOpenSSL.cmake b/cmake/FindWrapOpenSSL.cmake
new file mode 100644
index 0000000000..6e80862258
--- /dev/null
+++ b/cmake/FindWrapOpenSSL.cmake
@@ -0,0 +1,21 @@
+# We can't create the same interface imported target multiple times, CMake will complain if we do
+# that. This can happen if the find_package call is done in multiple different subdirectories.
+if(TARGET WrapOpenSSL::WrapOpenSSL)
+    set(WrapOpenSSL_FOUND ON)
+    return()
+endif()
+
+set(WrapOpenSSL_FOUND OFF)
+
+# Reuse logic from the headers find script.
+find_package(WrapOpenSSLHeaders ${WrapOpenSSL_FIND_VERSION})
+
+if(OpenSSL_FOUND)
+    set(WrapOpenSSL_FOUND ON)
+
+    add_library(WrapOpenSSL::WrapOpenSSL INTERFACE IMPORTED)
+    target_link_libraries(WrapOpenSSL::WrapOpenSSL INTERFACE OpenSSL::SSL)
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(WrapOpenSSL DEFAULT_MSG WrapOpenSSL_FOUND)
diff --git a/cmake/FindWrapOpenSSLHeaders.cmake b/cmake/FindWrapOpenSSLHeaders.cmake
new file mode 100644
index 0000000000..52e6df3b0a
--- /dev/null
+++ b/cmake/FindWrapOpenSSLHeaders.cmake
@@ -0,0 +1,34 @@
+# We can't create the same interface imported target multiple times, CMake will complain if we do
+# that. This can happen if the find_package call is done in multiple different subdirectories.
+if(TARGET WrapOpenSSLHeaders::WrapOpenSSLHeaders)
+    set(WrapOpenSSLHeaders_FOUND ON)
+    return()
+endif()
+
+set(WrapOpenSSLHeaders_FOUND OFF)
+
+# When cross-compiling (to Android for example), we need to add the OPENSSL_ROOT_DIR as a root path,
+# otherwise the value would just be appended to the sysroot, which is wrong.
+if(OPENSSL_ROOT_DIR)
+    set(__find_wrap_openssl_headers_backup_root_dir "${CMAKE_FIND_ROOT_PATH}")
+    list(APPEND CMAKE_FIND_ROOT_PATH "${OPENSSL_ROOT_DIR}")
+endif()
+
+find_package(OpenSSL ${WrapOpenSSLHeaders_FIND_VERSION})
+
+if(OPENSSL_ROOT_DIR)
+    set(CMAKE_FIND_ROOT_PATH "${__find_wrap_openssl_headers_backup_root_dir}")
+endif()
+
+# We are interested only in include headers. The libraries might be missing, so we can't check the
+# _FOUND variable.
+if(OPENSSL_INCLUDE_DIR)
+    set(WrapOpenSSLHeaders_FOUND ON)
+
+    add_library(WrapOpenSSLHeaders::WrapOpenSSLHeaders INTERFACE IMPORTED)
+    target_include_directories(WrapOpenSSLHeaders::WrapOpenSSLHeaders INTERFACE
+        ${OPENSSL_INCLUDE_DIR})
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(WrapOpenSSLHeaders DEFAULT_MSG WrapOpenSSLHeaders_FOUND)