Update gcc dependencies to gcc@9

[sjackman]

1. Bump revision if present or otherwise add revision 1
2. Change depends_on "gcc" or depends_on "gcc@8" to depends_on "gcc@9.

• arcs arcs: Bump revision for gcc@9 #1184
• arks
• bali-phy
• bamm
• biobloomtools
• bracken
• canu
• centrifuge
• dida
• discovardenovo
• ema ema: Bump revision for gcc@9 #1185
• fastani fastani 1.31 #1088 to use libomp
• gappa
• gfakluge
• hh-suite
• idba idba: Bump revision for gcc@9 #1305
• iqtree
• iqtree2
• kmc
• kraken
• kraken2
• megahit
• metabat
• mpboot
• nanopolish
• ngmerge
• ntcard
• ntedit
• nthits
• parasail
• portcullis
• pplacer
• r8s
• raptor
• raxml
• seqan@3
• stacks
• trinity
• vcflib
• viennarna
• vt
• wish