cmake: use `STREQUAL` to detect Linux

Instead of `MATCHES`.
To sync with another check that already used `STREQUAL`.

Closes #15855

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2edb8d09887dcb4593b071360d4dda3b9d6f7071..45aea19456b74946e0733ee6b1a629d2790c521d 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -225,7 +225,7 @@ cmake_dependent_option(ENABLE_THREADED_RESOLVER "Enable threaded DNS lookup"
 
 include(PickyWarnings)
 
-if(CMAKE_SYSTEM_NAME MATCHES "Linux")
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D_GNU_SOURCE")  # Required for sendmmsg()
 endif()