[LibWebRTC] Unreviewed, build fix for Linux after 276708@main

https://bugs.webkit.org/show_bug.cgi?id=271696

CMake was failing because there was an attempt to set 'webrtc' when it
was not yet defined. Move faulting lines below, once 'webrtc' is already
defined.

* Source/ThirdParty/libwebrtc/CMakeLists.txt:

Canonical link: https://commits.webkit.org/276724@main

Author: dpino

Source/ThirdParty/libwebrtc/CMakeLists.txt

@@ -2169,10 +2169,7 @@ else ()
             Source/webrtc/modules/audio_device/linux/audio_mixer_manager_pulse_linux.cc
             Source/webrtc/modules/audio_device/linux/pulseaudiosymboltable_linux.cc
         )
-        target_include_directories(webrtc PRIVATE ${LibPulse_INCLUDE_DIRS})
-        target_compile_options(webrtc PRIVATE ${LibPulse_COMPILE_OPTIONS})
     endif ()
-
 endif ()
 
 add_library(webrtc STATIC ${webrtc_SOURCES})
@@ -2303,6 +2300,10 @@ else ()
 endif ()
 
 target_include_directories(webrtc ${webrtc_INCLUDE_DIRECTORIES})
+if (LIBPULSE_FOUND)
+    target_include_directories(webrtc PRIVATE ${LibPulse_INCLUDE_DIRS})
+    target_compile_options(webrtc PRIVATE ${LibPulse_COMPILE_OPTIONS})
+endif ()
 
 # libsrtp package compilation
 set(libsrtp_SOURCES