Fix build errors with WENDELIN-MASTER-DEV

I noticed by accident that tests for `software/wendelin/software-dev.cfg` where failing because buildout was picking eggs:

```
Installing eggs.
While:
  Installing eggs.
  Getting distribution for 'scikit-learn'.
Error: Picked: scikit-learn = 0.19.2
Failed to run buildout profile in directory '/srv/slapgrid/slappart7/srv/testnode/acv/soft/78ae8a6d8b0639addb22de2c7c96af63'
```

Turned out it was a problem with usage of `zc.recipe.egg:develop`

There was also a problem which `${gcc-fortran:}` that does not exist anymore.

/reviewed-on !395

component/PyWavelets/buildout.cfg

 [buildout]
 extends =
+  ../gcc/buildout.cfg
   ../numpy/openblas.cfg
   ../cython/buildout.cfg
   ../scipy/buildout.cfg
@@ -41,6 +42,6 @@ setup-eggs =
   ${numpy:egg}
   ${scipy:egg}
 rpath =
-  ${gcc-fortran:location}/lib
-  ${gcc-fortran:location}/lib64
+  ${gcc:location}/lib
+  ${gcc:location}/lib64
   ${openblas:location}/lib

component/scikit-image/buildout.cfg

 [buildout]
 extends =
+  ../gcc/buildout.cfg
   ../numpy/openblas.cfg
   ../cython/buildout.cfg
   ../scipy/buildout.cfg
@@ -49,6 +50,6 @@ setup-eggs =
   ${pillow-python:egg}
   networkx
 rpath =
-  ${gcc-fortran:location}/lib
-  ${gcc-fortran:location}/lib64
+  ${gcc:location}/lib
+  ${gcc:location}/lib64
   ${openblas:location}/lib

component/scikit-learn/buildout.cfg

 [buildout]
 extends =
+  ../gcc/buildout.cfg
   ../cython/buildout.cfg
   ../numpy/openblas.cfg
   ../scipy/buildout.cfg
@@ -40,6 +41,6 @@ setup-eggs =
   ${numpy:egg}
   ${scipy:egg}
 rpath =
-  ${gcc-fortran:location}/lib
-  ${gcc-fortran:location}/lib64
+  ${gcc:location}/lib
+  ${gcc:location}/lib64
   ${openblas:location}/lib

software/wendelin/software-dev.cfg

@@ -22,4 +22,4 @@ scikit-learn =
 
 # install scikit-learn git clone
 [scikit-learn]
-<= scikit-learn-develop
+depends = ${scikit-learn-develop:recipe}