yet another attempt at finding FFTW

Author: mrodrig6

toolchain/cmake/regular/FindFFTW.cmake

@@ -1,39 +1,33 @@
-# Robust FFTW finder: supports pkg-config, system installs, and manual hints
+# FindFFTW.cmake — robust FFTW detection for system installs & CI
 
 find_package(PkgConfig QUIET)
 if(PkgConfig_FOUND)
   pkg_check_modules(PC_FFTW QUIET fftw3)
 endif()
 
-# Search locations
-set(FFTW_HINTED_INCLUDE
-  $ENV{FFTW_INCLUDE_DIR}
-  ${PC_FFTW_INCLUDE_DIRS}
-  /usr/include
-  /usr/local/include
-)
-
-set(FFTW_HINTED_LIBRARY
-  $ENV{FFTW_LIBRARY}
-  ${PC_FFTW_LIBRARY_DIRS}
-  /usr/lib
-  /usr/lib64
-  /usr/local/lib
-  /usr/lib/x86_64-linux-gnu
-)
-
-# Locate paths
+# Search for the include directory
 find_path(FFTW_INCLUDE_DIR
   NAMES fftw3.h
-  HINTS ${FFTW_HINTED_INCLUDE}
+  HINTS
+    ${PC_FFTW_INCLUDE_DIRS}
+    /usr/include
+    /usr/local/include
+    /opt/include
 )
 
+# Search for the library
 find_library(FFTW_LIBRARY
   NAMES fftw3
-  HINTS ${FFTW_HINTED_LIBRARY}
+  HINTS
+    ${PC_FFTW_LIBRARY_DIRS}
+    /usr/lib
+    /usr/lib64
+    /usr/local/lib
+    /opt/lib
+    /usr/lib/x86_64-linux-gnu
 )
 
-# Safe version check
+# Import handling
 include(FindPackageHandleStandardArgs)
 
 if(DEFINED PC_FFTW_VERSION AND NOT "${PC_FFTW_VERSION}" STREQUAL "")
@@ -49,7 +43,7 @@ endif()
 
 mark_as_advanced(FFTW_INCLUDE_DIR FFTW_LIBRARY)
 
-# Optional modern target
+# Optional modern target alias
 if(FFTW_FOUND AND NOT TARGET FFTW::FFTW)
   add_library(FFTW::FFTW UNKNOWN IMPORTED)
   set_target_properties(FFTW::FFTW PROPERTIES