Testsuite: Fix globbing command for all-headers tests, cleanup code
Testsuite: Fix globbing command for all-headers tests, cleanup code

Turns out that globbing together a full path and manually extracting
relative paths is not the best idea. Clean up this mess by using
FILE(GLOB_RECURSE [base path] [...]) that produces nice relative paths.

mac-a/dealii,mac-a/dealii,ibkim11/dealii,natashasharma/dealii,jperryhouts/dealii,maieneuro/dealii,nicolacavallini/dealii,JaeryunYim/dealii,spco/dealii,mtezzele/dealii,naliboff/dealii,JaeryunYim/dealii,lpolster/dealii,kalj/dealii,flow123d/dealii,lpolster/dealii,msteigemann/dealii,maieneuro/dealii,lue/dealii,jperryhouts/dealii,natashasharma/dealii,rrgrove6/dealii,spco/dealii,andreamola/dealii,ibkim11/dealii,maieneuro/dealii,andreamola/dealii,shakirbsm/dealii,natashasharma/dealii,ESeNonFossiIo/dealii,lue/dealii,angelrca/dealii,pesser/dealii,shakirbsm/dealii,natashasharma/dealii,johntfoster/dealii,adamkosik/dealii,nicolacavallini/dealii,ESeNonFossiIo/dealii,ibkim11/dealii,spco/dealii,msteigemann/dealii,rrgrove6/dealii,mac-a/dealii,kalj/dealii,pesser/dealii,angelrca/dealii,adamkosik/dealii,EGP-CIG-REU/dealii,pesser/dealii,gpitton/dealii,nicolacavallini/dealii,sairajat/dealii,adamkosik/dealii,mac-a/dealii,angelrca/dealii,ESeNonFossiIo/dealii,danshapero/dealii,angelrca/dealii,lue/dealii,EGP-CIG-REU/dealii,kalj/dealii,sriharisundar/dealii,naliboff/dealii,mac-a/dealii,sriharisundar/dealii,andreamola/dealii,JaeryunYim/dealii,danshapero/dealii,EGP-CIG-REU/dealii,johntfoster/dealii,YongYang86/dealii,rrgrove6/dealii,pesser/dealii,sriharisundar/dealii,nicolacavallini/dealii,sriharisundar/dealii,gpitton/dealii,natashasharma/dealii,EGP-CIG-REU/dealii,naliboff/dealii,EGP-CIG-REU/dealii,lpolster/dealii,johntfoster/dealii,jperryhouts/dealii,sairajat/dealii,kalj/dealii,maieneuro/dealii,flow123d/dealii,sriharisundar/dealii,maieneuro/dealii,danshapero/dealii,ESeNonFossiIo/dealii,gpitton/dealii,msteigemann/dealii,rrgrove6/dealii,gpitton/dealii,mac-a/dealii,danshapero/dealii,mtezzele/dealii,angelrca/dealii,YongYang86/dealii,rrgrove6/dealii,ESeNonFossiIo/dealii,kalj/dealii,pesser/dealii,danshapero/dealii,danshapero/dealii,shakirbsm/dealii,gpitton/dealii,naliboff/dealii,johntfoster/dealii,spco/dealii,andreamola/dealii,msteigemann/dealii,adamkosik/dealii,lue/dealii,adamkosik/dealii,JaeryunYim/dealii,shakirbsm/dealii,shakirbsm/dealii,andreamola/dealii,sriharisundar/dealii,gpitton/dealii,Arezou-gh/dealii,sairajat/dealii,Arezou-gh/dealii,mtezzele/dealii,YongYang86/dealii,shakirbsm/dealii,mtezzele/dealii,naliboff/dealii,lpolster/dealii,lpolster/dealii,jperryhouts/dealii,EGP-CIG-REU/dealii,lue/dealii,YongYang86/dealii,pesser/dealii,YongYang86/dealii,spco/dealii,flow123d/dealii,lue/dealii,gpitton/dealii,nicolacavallini/dealii,ibkim11/dealii,ibkim11/dealii,angelrca/dealii,sairajat/dealii,EGP-CIG-REU/dealii,Arezou-gh/dealii,JaeryunYim/dealii,mtezzele/dealii,YongYang86/dealii,kalj/dealii,sairajat/dealii,jperryhouts/dealii,danshapero/dealii,adamkosik/dealii,natashasharma/dealii,msteigemann/dealii,angelrca/dealii,flow123d/dealii,ibkim11/dealii,lpolster/dealii,lue/dealii,Arezou-gh/dealii,jperryhouts/dealii,spco/dealii,flow123d/dealii,sairajat/dealii,ESeNonFossiIo/dealii,JaeryunYim/dealii,Arezou-gh/dealii,johntfoster/dealii,naliboff/dealii,rrgrove6/dealii,sairajat/dealii,JaeryunYim/dealii,Arezou-gh/dealii,johntfoster/dealii,rrgrove6/dealii,maieneuro/dealii,flow123d/dealii,sriharisundar/dealii,naliboff/dealii,mtezzele/dealii,Arezou-gh/dealii,mac-a/dealii,msteigemann/dealii,johntfoster/dealii,nicolacavallini/dealii,andreamola/dealii,shakirbsm/dealii,mtezzele/dealii,adamkosik/dealii,maieneuro/dealii,jperryhouts/dealii,kalj/dealii,msteigemann/dealii,ibkim11/dealii,ESeNonFossiIo/dealii,pesser/dealii,YongYang86/dealii,spco/dealii,andreamola/dealii,lpolster/dealii,natashasharma/dealii,flow123d/dealii,nicolacavallini/dealii