COMP: Fix ITK-HDF5 C flags for non-GNU compilers
COMP: Fix ITK-HDF5 C flags for non-GNU compilers

Do not hard-code flags like

  -std=c99 -fomit-frame-pointer -finline-functions -fno-common

for all non-Windows compilers.  Add the flags only for GNU C.

cpatrick/ITK-RemoteIO,BlueBrain/ITK,BlueBrain/ITK,eile/ITK,msmolens/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,itkvideo/ITK,atsnyder/ITK,CapeDrew/DCMTK-ITK,eile/ITK,fbudin69500/ITK,msmolens/ITK,malaterre/ITK,paulnovo/ITK,stnava/ITK,Kitware/ITK,rhgong/itk-with-dom,GEHC-Surgery/ITK,wkjeong/ITK,rhgong/itk-with-dom,paulnovo/ITK,vfonov/ITK,spinicist/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,fedral/ITK,zachary-williamson/ITK,cpatrick/ITK-RemoteIO,fedral/ITK,rhgong/itk-with-dom,hjmjohnson/ITK,richardbeare/ITK,LucHermitte/ITK,richardbeare/ITK,cpatrick/ITK-RemoteIO,vfonov/ITK,msmolens/ITK,wkjeong/ITK,Kitware/ITK,hjmjohnson/ITK,hjmjohnson/ITK,itkvideo/ITK,jcfr/ITK,stnava/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,atsnyder/ITK,malaterre/ITK,hinerm/ITK,fuentesdt/InsightToolkit-dev,eile/ITK,zachary-williamson/ITK,rhgong/itk-with-dom,heimdali/ITK,paulnovo/ITK,CapeDrew/DITK,CapeDrew/DCMTK-ITK,jcfr/ITK,jmerkow/ITK,hinerm/ITK,msmolens/ITK,heimdali/ITK,LucHermitte/ITK,cpatrick/ITK-RemoteIO,hendradarwin/ITK,atsnyder/ITK,fbudin69500/ITK,biotrump/ITK,spinicist/ITK,GEHC-Surgery/ITK,itkvideo/ITK,ajjl/ITK,eile/ITK,BlueBrain/ITK,CapeDrew/DCMTK-ITK,GEHC-Surgery/ITK,PlutoniumHeart/ITK,CapeDrew/DCMTK-ITK,zachary-williamson/ITK,fbudin69500/ITK,fedral/ITK,ajjl/ITK,thewtex/ITK,jcfr/ITK,CapeDrew/DITK,InsightSoftwareConsortium/ITK,InsightSoftwareConsortium/ITK,stnava/ITK,fbudin69500/ITK,LucasGandel/ITK,blowekamp/ITK,hinerm/ITK,fedral/ITK,zachary-williamson/ITK,hendradarwin/ITK,Kitware/ITK,msmolens/ITK,itkvideo/ITK,cpatrick/ITK-RemoteIO,LucHermitte/ITK,PlutoniumHeart/ITK,spinicist/ITK,hjmjohnson/ITK,hjmjohnson/ITK,BlueBrain/ITK,PlutoniumHeart/ITK,BlueBrain/ITK,fedral/ITK,msmolens/ITK,msmolens/ITK,spinicist/ITK,fuentesdt/InsightToolkit-dev,GEHC-Surgery/ITK,CapeDrew/DCMTK-ITK,hinerm/ITK,jmerkow/ITK,LucasGandel/ITK,jmerkow/ITK,biotrump/ITK,LucHermitte/ITK,fuentesdt/InsightToolkit-dev,paulnovo/ITK,jmerkow/ITK,heimdali/ITK,malaterre/ITK,zachary-williamson/ITK,jmerkow/ITK,spinicist/ITK,hjmjohnson/ITK,paulnovo/ITK,paulnovo/ITK,stnava/ITK,hinerm/ITK,heimdali/ITK,biotrump/ITK,hendradarwin/ITK,heimdali/ITK,InsightSoftwareConsortium/ITK,paulnovo/ITK,fuentesdt/InsightToolkit-dev,fbudin69500/ITK,malaterre/ITK,wkjeong/ITK,rhgong/itk-with-dom,vfonov/ITK,ajjl/ITK,msmolens/ITK,LucHermitte/ITK,hinerm/ITK,zachary-williamson/ITK,paulnovo/ITK,heimdali/ITK,wkjeong/ITK,eile/ITK,vfonov/ITK,fuentesdt/InsightToolkit-dev,stnava/ITK,CapeDrew/DCMTK-ITK,vfonov/ITK,jcfr/ITK,InsightSoftwareConsortium/ITK,hendradarwin/ITK,thewtex/ITK,LucHermitte/ITK,biotrump/ITK,richardbeare/ITK,ajjl/ITK,blowekamp/ITK,rhgong/itk-with-dom,PlutoniumHeart/ITK,vfonov/ITK,jcfr/ITK,stnava/ITK,BRAINSia/ITK,ajjl/ITK,malaterre/ITK,thewtex/ITK,malaterre/ITK,hinerm/ITK,jmerkow/ITK,thewtex/ITK,CapeDrew/DITK,richardbeare/ITK,CapeDrew/DITK,heimdali/ITK,cpatrick/ITK-RemoteIO,CapeDrew/DITK,Kitware/ITK,jcfr/ITK,hjmjohnson/ITK,richardbeare/ITK,blowekamp/ITK,spinicist/ITK,jcfr/ITK,rhgong/itk-with-dom,fuentesdt/InsightToolkit-dev,BlueBrain/ITK,hendradarwin/ITK,fuentesdt/InsightToolkit-dev,biotrump/ITK,wkjeong/ITK,thewtex/ITK,fedral/ITK,PlutoniumHeart/ITK,GEHC-Surgery/ITK,blowekamp/ITK,BRAINSia/ITK,CapeDrew/DCMTK-ITK,GEHC-Surgery/ITK,atsnyder/ITK,fedral/ITK,vfonov/ITK,LucHermitte/ITK,thewtex/ITK,zachary-williamson/ITK,malaterre/ITK,eile/ITK,stnava/ITK,biotrump/ITK,stnava/ITK,itkvideo/ITK,stnava/ITK,heimdali/ITK,BRAINSia/ITK,CapeDrew/DITK,hinerm/ITK,CapeDrew/DITK,ajjl/ITK,atsnyder/ITK,PlutoniumHeart/ITK,PlutoniumHeart/ITK,richardbeare/ITK,jmerkow/ITK,BRAINSia/ITK,LucasGandel/ITK,jmerkow/ITK,InsightSoftwareConsortium/ITK,CapeDrew/DCMTK-ITK,Kitware/ITK,eile/ITK,blowekamp/ITK,fbudin69500/ITK,spinicist/ITK,hendradarwin/ITK,blowekamp/ITK,itkvideo/ITK,fuentesdt/InsightToolkit-dev,hinerm/ITK,blowekamp/ITK,spinicist/ITK,atsnyder/ITK,malaterre/ITK,itkvideo/ITK,PlutoniumHeart/ITK,itkvideo/ITK,vfonov/ITK,hendradarwin/ITK,Kitware/ITK,CapeDrew/DITK,fuentesdt/InsightToolkit-dev,itkvideo/ITK,BlueBrain/ITK,hendradarwin/ITK,CapeDrew/DCMTK-ITK,ajjl/ITK,LucasGandel/ITK,wkjeong/ITK,biotrump/ITK,fbudin69500/ITK,vfonov/ITK,jcfr/ITK,blowekamp/ITK,atsnyder/ITK,LucasGandel/ITK,zachary-williamson/ITK,richardbeare/ITK,LucasGandel/ITK,cpatrick/ITK-RemoteIO,wkjeong/ITK,spinicist/ITK,LucHermitte/ITK,atsnyder/ITK,BRAINSia/ITK,wkjeong/ITK,malaterre/ITK,fbudin69500/ITK,zachary-williamson/ITK,eile/ITK,GEHC-Surgery/ITK,rhgong/itk-with-dom,biotrump/ITK,BRAINSia/ITK,fedral/ITK,Kitware/ITK,LucasGandel/ITK,ajjl/ITK,GEHC-Surgery/ITK,BRAINSia/ITK,eile/ITK,CapeDrew/DITK,atsnyder/ITK