PHP/SearchLibraries: Remove -l flags from libraries

If libraries are passed with -l flags (for example, `-ldl`), they should
be interpreted as library names for consistency as already used across
the CMake.

Author: petk

cmake/cmake/modules/PHP/SearchLibraries.cmake

@@ -69,6 +69,9 @@ The arguments are:
   a macro definition. It would not be found using the other two commands because
   they don't include required headers.
 
+  Any `-l` strings prepended to the provided libraries are removed in the
+  results. For example, `-ldl` will be interpreted as `dl`.
+
 * `VARIABLE <variable>`
 
   Optional. Name of an internal cache variable where the result of the check is
@@ -274,6 +277,9 @@ function(php_search_libraries)
   foreach(library IN LISTS parsed_LIBRARIES)
     unset(${parsed_VARIABLE} CACHE)
 
+    # If library was given as -l<library-name>, remove the linker flag.
+    string(REGEX REPLACE "^-l" "" library "${library}")
+
     if(NOT CMAKE_REQUIRED_QUIET)
       message(CHECK_START "Looking for ${symbol} in ${library}")
     endif()