pgplot: Correct build error with shared libraries (#27154)

When building pgplot as shared library, dependencies need to be listed explicitly.

var/spack/repos/builtin/packages/pgplot/g77_gcc.conf.patch

@@ -78,7 +78,7 @@
  
  # Mandatory.
  # On systems that have a ranlib utility, put "ranlib" here. On other
-@@ -108,7 +108,7 @@
+@@ -108,16 +108,16 @@
  # Optional: Needed if SHARED_LIB is set.
  # How to create a shared library from a trailing list of object files.
   
@@ -87,3 +87,13 @@
  
  # Optional:
  # On systems such as Solaris 2.x, that allow specification of the
+ # libraries that a shared library needs to be linked with when a
+ # program that uses it is run, this variable should contain the
+ # library-specification flags used to specify these libraries to
+ # $SHARED_LD
+  
+-   SHARED_LIB_LIBS=""
++   SHARED_LIB_LIBS="@SHARED_LIB_LIBS@"
+ 
+ # Optional:
+ # Compiler name used on Next systems to compile objective-C files.

var/spack/repos/builtin/packages/pgplot/package.py

@@ -7,7 +7,7 @@
 
 
 class Pgplot(MakefilePackage):
-    """PGPLOT Graphics Subroutine Library
+    """PGPLOT Graphics Subroutine Library.
 
     The PGPLOT Graphics Subroutine Library is a Fortran- or
     C-callable, device-independent graphics package for making
@@ -51,6 +51,12 @@ class Pgplot(MakefilePackage):
 
     def edit(self, spec, prefix):
 
+        libs = ''
+        if '+X' in spec:
+            libs += ' ' + self.spec['X11'].libs.ld_flags
+        if '+png' in spec:
+            libs += ' ' + self.spec['libpng'].libs.ld_flags
+
         if spec.satisfies('%gcc'):
             fib = " -fallow-invalid-boz" if spec.satisfies('%gcc@10:') else ""
 
@@ -61,9 +67,10 @@ def edit(self, spec, prefix):
                 '@CFLAGD@': "-O2",
                 '@FCOMPL@': spack_fc,
                 '@FFLAGC@': "-Wall -fPIC -O -ffixed-line-length-none" + fib,
-                '@FFLAGD@': "-fno-backslash",
+                '@FFLAGD@': libs + " -fno-backslash",
-                '@LIBS@': "-lgfortran",
+                '@LIBS@': libs + " -lgfortran",
-                '@SHARED_LD@': spack_cc + " -shared -o $SHARED_LIB -lgfortran"
+                '@SHARED_LD@': spack_cc + " -shared -o $SHARED_LIB",
+                '@SHARED_LIB_LIBS@': libs + " -lgfortran",
             }
         elif spec.satisfies('%intel'):
             sub = {
@@ -72,9 +79,10 @@ def edit(self, spec, prefix):
                 '@CFLAGD@': "-O2 -lifcore -lifport",
                 '@FCOMPL@': spack_fc,
                 '@FFLAGC@': "-fPIC",
-                '@FFLAGD@': "-nofor-main",
+                '@FFLAGD@': libs + " -nofor-main",
-                '@LIBS@': "-nofor-main -lifcore -lifport",
+                '@LIBS@': libs + " -nofor-main -lifcore -lifport",
-                '@SHARED_LD@': spack_cc + " -shared -o $SHARED_LIB"
+                '@SHARED_LD@': spack_cc + " -shared -o $SHARED_LIB",
+                '@SHARED_LIB_LIBS@': libs + " -nofor-main -lifcore -lifport",
             }
 
         conf = join_path(
@@ -91,14 +99,12 @@ def edit(self, spec, prefix):
             enable_driver('! XWDRIV 1 /XWINDOW')
             enable_driver('! XWDRIV 2 /XSERVE')
 
-            sub['@FFLAGD@'] += ' -L{0} -lX11'.format(self.spec['libx11'].prefix.lib)
-            sub['@LIBS@'] += ' -L{0} -lX11'.format(self.spec['libx11'].prefix.lib)
-
         if '+png' in spec:
             enable_driver('! PNDRIV 1 /PNG')
 
             filter_file('pndriv.o : ./png.h ./pngconf.h ./zlib.h ./zconf.h',
-                        'pndriv.o :', 'makemake')
+                        'pndriv.o :',
+                        'makemake')
 
         # Alwasy enable PS and LATEX since they are not depending on other libraries.
         enable_driver('! PSDRIV 1 /PS')
@@ -115,8 +121,10 @@ def edit(self, spec, prefix):
             filter_file(key, value, conf)
 
     def setup_build_environment(self, env):
+        if '+X' in self.spec:
+            env.append_flags('LIBS', self.spec['X11'].libs.ld_flags)
         if '+png' in self.spec:
-            env.set('LIBS', self.spec['libpng'].libs.ld_flags)
+            env.append_flags('LIBS', self.spec['libpng'].libs.ld_flags)
 
     def build(self, spec, prefix):
         makemake = which('./makemake')