Remove dependency on libpng

There is an import of `png.h` that turns out to not be used.
I have patched to remove this and SQuadGen now builds and runs
without requiring `libpng`.

recipes/squadgen/0001-remove-png-h.patch

@@ -0,0 +1,20 @@
+diff -ruN squadgen-1.2.1/src/SQuadGen.cpp squadgen-1.2.1-patch/src/SQuadGen.cpp
+--- squadgen-1.2.1/src/SQuadGen.cpp	2024-05-11 15:31:02.000000000 -0600
++++ squadgen-1.2.1-patch/src/SQuadGen.cpp	2024-05-12 11:20:44.022644614 -0600
+@@ -14,7 +14,6 @@
+ ///		or implied warranty.
+ ///	</remarks>
+
+-#include <png.h>
+ #include "netcdfcpp.h"
+
+ #include <string>
+@@ -195,7 +194,7 @@
+ 	if ((nRefinementLevel > 0) &&
+ 		((strRefineRect != "") || (strRefineFile != "") || (fLoadCSRefinementMap))
+ 	) {
+-		int nCommandLineCount = 
++		int nCommandLineCount =
+ 			  ((strRefineRect != "")?(1):(0))
+ 			+ ((strRefineFile != "")?(1):(0))
+ 			+ (fLoadCSRefinementMap?(1):(0));

recipes/squadgen/CMakeLists.txt

@@ -13,10 +13,6 @@ find_package(NETCDF REQUIRED)
 message(STATUS "netcdf_c_incdir=${netcdf_c_incdir}")
 message(STATUS "netcdf_c_libs=${netcdf_c_libs}")
 
-find_package(PNG REQUIRED)
-message(STATUS "PNG_INCLUDE_DIR=${PNG_INCLUDE_DIR}")
-message(STATUS "PNG_LIBRARIES=${PNG_LIBRARIES}")
-
 SET(SRC ${CMAKE_SOURCE_DIR}/src)
 set(SQUADGEN_SRC ${SRC}/SQuadGen.cpp
                  ${SRC}/GridElements.cpp
@@ -34,11 +30,10 @@ set(SQUADGEN_SRC ${SRC}/SQuadGen.cpp
                  ${SRC}/netcdf.cpp
                  ${SRC}/ncvalues.cpp)
 
-include_directories(${PNG_INCLUDE_DIR})
 include_directories(${netcdf_c_incdir})
 
 include_directories(${SRC})
 add_executable(SQuadGen ${SQUADGEN_SRC})
-target_link_libraries(SQuadGen PUBLIC ${netcdf_c_libs} ${PNG_LIBRARIES})
+target_link_libraries(SQuadGen ${netcdf_c_libs})
 
 install(TARGETS SQuadGen DESTINATION bin)

recipes/squadgen/build.sh

@@ -5,6 +5,9 @@ set -e
 
 cp -r ${RECIPE_DIR}/cmake ${RECIPE_DIR}/cmake_macros ${RECIPE_DIR}/CMakeLists.txt .
 
+# remove static libpng and zlib to prevent static linking
+rm -rf ${PREFIX}/lib/libpng.a ${PREFIX}/lib/libz.a
+
 rm -rf build
 mkdir build
 cd build

recipes/squadgen/meta.yaml

@@ -8,12 +8,12 @@ package:
 source:
   url: https://github.com/ClimateGlobalChange/squadgen/archive/refs/tags/v{{ version }}.tar.gz
   sha256: a39f9f467563e796c1b0a53c7bf7d046f50110a030d92350754a60ada4eda053
+  patches:
+    - 0001-remove-png-h.patch
 
 build:
   skip: true  # [not linux]
   number: 0
-  ignore_run_exports:
-    - libpng
 
 requirements:
   build:
@@ -25,7 +25,6 @@ requirements:
   host:
     - libnetcdf
     - libnetcdf * nompi_*
-    - libpng
 
 test:
   files: