Simplify building nix-perl in nix-shell

perl/Makefile

@@ -1,6 +1,6 @@
 makefiles = local.mk
 
-GLOBAL_CXXFLAGS += -std=c++14 -g -Wall -include nix/config.h
+GLOBAL_CXXFLAGS += -std=c++14 -g -Wall
 
 -include Makefile.config
 

perl/configure.ac

@@ -98,7 +98,7 @@ for name in $ac_subst_vars; do
 done
 
 rm -f Makefile.config
-ln -s ../mk mk
+ln -sfn ../mk mk
 
 AC_CONFIG_FILES([])
 AC_OUTPUT

perl/lib/Nix/Store.xs

@@ -1,3 +1,5 @@
+#include "config.h"
+
 #include "EXTERN.h"
 #include "perl.h"
 #include "XSUB.h"

perl/local.mk

@@ -20,11 +20,11 @@ Store_DIR := lib/Nix
 Store_SOURCES := $(Store_DIR)/Store.cc
 
 Store_CXXFLAGS = \
-  -I$(shell $(perl) -e 'use Config; print $$Config{archlibexp};')/CORE \
+  $(NIX_CFLAGS) \
+  -I$(shell perl -e 'use Config; print $$Config{archlibexp};')/CORE \
   -D_FILE_OFFSET_BITS=64 \
   -Wno-unknown-warning-option -Wno-unused-variable -Wno-literal-suffix \
-  -Wno-reserved-user-defined-literal -Wno-duplicate-decl-specifier -Wno-pointer-bool-conversion \
-  $(NIX_CFLAGS)
+  -Wno-reserved-user-defined-literal -Wno-duplicate-decl-specifier -Wno-pointer-bool-conversion
 
 Store_LDFLAGS := $(SODIUM_LIBS) $(NIX_LIBS)
 

shell.nix

@@ -17,6 +17,10 @@ with import <nixpkgs> {};
       })
       autoreconfHook
       readline
+
+      # For nix-perl
+      perl
+      perlPackages.DBDSQLite
     ];
 
   configureFlags =
@@ -30,6 +34,9 @@ with import <nixpkgs> {};
 
   shellHook =
     ''
-      configureFlags+=" --prefix=$(pwd)/inst"
+      export prefix=$(pwd)/inst
+      configureFlags+=" --prefix=prefix"
+      PKG_CONFIG_PATH=$prefix/lib/pkgconfig:$PKG_CONFIG_PATH
+      PATH=$prefix/bin:$PATH
     '';
 }