saga: Fix compiling on Darwin (NixOS#384655)

Author: Aleksanaa

pkgs/by-name/sa/saga/darwin-patch-1.patch

@@ -0,0 +1,30 @@
+commit 3bbd15676dfc077d7836e9d51810c1d6731f5789
+Author: Palmer Cox <p@lmercox.com>
+Date:   Sun Feb 23 16:41:18 2025 -0500
+
+    Fix copy/paste error in FindPostgres.cmake
+    
+    In f51c6b1513e312002c108fe87d26e33c48671406, EXEC_PROGRAM was changed to
+    execute_process. As part of that, it looks like the second and third
+    invocations were accidentally changed.
+
+diff --git a/saga-gis/cmake/modules/FindPostgres.cmake b/saga-gis/cmake/modules/FindPostgres.cmake
+index f22806fd9..a4b6ec9ac 100644
+--- a/cmake/modules/FindPostgres.cmake
++++ b/cmake/modules/FindPostgres.cmake
+@@ -77,13 +77,13 @@ ELSE(WIN32)
+       SET(POSTGRES_INCLUDE_DIR ${PG_TMP} CACHE STRING INTERNAL)
+ 
+       # set LIBRARY_DIR
+-      execute_process(COMMAND ${POSTGRES_CONFIG} --includedir
++      execute_process(COMMAND ${POSTGRES_CONFIG} --libdir
+         OUTPUT_VARIABLE PG_TMP
+         OUTPUT_STRIP_TRAILING_WHITESPACE)
+       IF (APPLE)
+         SET(POSTGRES_LIBRARY ${PG_TMP}/libpq.dylib CACHE STRING INTERNAL)
+       ELSEIF (CYGWIN)
+-        execute_process(COMMAND ${POSTGRES_CONFIG} --includedir
++        execute_process(COMMAND ${POSTGRES_CONFIG} --libs
+           OUTPUT_VARIABLE PG_TMP
+           OUTPUT_STRIP_TRAILING_WHITESPACE)
+ 

pkgs/by-name/sa/saga/darwin-patch-2.patch

@@ -0,0 +1,24 @@
+commit eb69f594ec439309432e87834bead5276b7dbc9b
+Author: Palmer Cox <p@lmercox.com>
+Date:   Sun Feb 23 16:45:34 2025 -0500
+
+    On Apple, use FIND_LIBRARY to locate libpq
+    
+    I think FIND_LIBRARY() is better than just relying on what pg_config
+    said its libdir was, since, depending on how libpq was installed, it may
+    or may not be in that directory. If its not, FIND_LIBRARY() is able to
+    find it in other locations.
+
+diff --git a/saga-gis/cmake/modules/FindPostgres.cmake b/saga-gis/cmake/modules/FindPostgres.cmake
+index a4b6ec9ac..65e7ac69b 100644
+--- a/cmake/modules/FindPostgres.cmake
++++ b/cmake/modules/FindPostgres.cmake
+@@ -81,7 +81,7 @@ ELSE(WIN32)
+         OUTPUT_VARIABLE PG_TMP
+         OUTPUT_STRIP_TRAILING_WHITESPACE)
+       IF (APPLE)
+-        SET(POSTGRES_LIBRARY ${PG_TMP}/libpq.dylib CACHE STRING INTERNAL)
++        FIND_LIBRARY(POSTGRES_LIBRARY NAMES pq libpq PATHS ${PG_TMP})
+       ELSEIF (CYGWIN)
+         execute_process(COMMAND ${POSTGRES_CONFIG} --libs
+           OUTPUT_VARIABLE PG_TMP

pkgs/by-name/sa/saga/package.nix

@@ -43,6 +43,14 @@ stdenv.mkDerivation rec {
 
   sourceRoot = "saga-${version}/saga-gis";
 
+  patches = [
+    # Patches from https://sourceforge.net/p/saga-gis/code/merge-requests/38/.
+    # These are needed to fix building on Darwin (technically the first is not
+    # required, but the second doesn't apply without it).
+    ./darwin-patch-1.patch
+    ./darwin-patch-2.patch
+  ];
+
   nativeBuildInputs = [
     cmake
     wrapGAppsHook3