runtime: set TLSG_IS_VARIABLE for android/arm64.
runtime: set TLSG_IS_VARIABLE for android/arm64.

On android, runtime.tls_g is a normal variable.
TLS offset is computed in x_cgo_inittls.

Change-Id: I18bc9a736d5fb2a89d0f798956c754e3c10d10e2
Reviewed-on: https://go-review.googlesource.com/17246
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

suncycheng/go,suncycheng/go,momchil-velikov/go,Cofyc/go,cyberroadie/go,vanloswang/go,ImJasonH/go,kim-racktop/go,derekmarcotte/go,Cofyc/go,ImJasonH/go,derekmarcotte/go,goodlang/good,cloudflare/go,Cofyc/go,cyberroadie/go,cyberroadie/go,golang/go,nawawi/go,akutz/go,vsekhar/elastic-go,polyverse-security/go,Endika/go,odeke-em/go,sndnvaps/go,codestation/go,fjballest/golang,linux-on-ibm-z/go,vsekhar/elastic-go,vanloswang/go,binarycrusader/go,mwhudson/go,Endika/go,ganboing/go-esx,theif519/go,vanloswang/go,mwhudson/go,Samurais/go,odeke-em/go,miolini/go,josharian/go,cloudflare/go,cloudflare/go,polyverse-security/go,ganboing/go-esx,binarycrusader/go,mwhudson/go,kim-racktop/go,Endika/go,ganboing/go-esx,4ad/go,binarycrusader/go,josharian/go,ganboing/go-esx,Samurais/go,akutz/go,derekmarcotte/go,nawawi/go,vsekhar/elastic-go,4ad/go,deft-code/go,polyverse-security/go,kim-racktop/go,ImJasonH/go,ganboing/go-esx,odeke-em/go,vsekhar/elastic-go,Samurais/go,momchil-velikov/go,vanloswang/go,suncycheng/go,sndnvaps/go,miolini/go,polyverse-security/go,nawawi/go,theif519/go,polyverse-security/go,odeke-em/go,golang/go,roth1002/go,vsekhar/elastic-go,odeke-em/go,kim-racktop/go,nawawi/go,derekmarcotte/go,sndnvaps/go,derekmarcotte/go,miolini/go,josharian/go,josharian/go,CAFxX/go,deft-code/go,momchil-velikov/go,4ad/go,momchil-velikov/go,Cofyc/go,Samurais/go,vanloswang/go,roth1002/go,ganboing/go-esx,ImJasonH/go,momchil-velikov/go,theif519/go,akutz/go,Cofyc/go,CAFxX/go,theif519/go,Samurais/go,fjballest/golang,codestation/go,Cofyc/go,suncycheng/go,polyverse-security/go,mwhudson/go,linux-on-ibm-z/go,polyverse-security/go,theif519/go,4ad/go,suncycheng/go,roth1002/go,4ad/go,kim-racktop/go,golang/go,christopher-henderson/Go,cloudflare/go,momchil-velikov/go,momchil-velikov/go,CAFxX/go,golang/go,roth1002/go,ganboing/go-esx,kim-racktop/go,4ad/go,CAFxX/go,linux-on-ibm-z/go,roth1002/go,deft-code/go,mwhudson/go,josharian/go,CAFxX/go,vanloswang/go,linux-on-ibm-z/go,4ad/go,golang/go,akutz/go,derekmarcotte/go,Samurais/go,fjballest/golang,miolini/go,josharian/go,mwhudson/go,vanloswang/go,linux-on-ibm-z/go,vsekhar/elastic-go,mwhudson/go,cloudflare/go,Endika/go,codestation/go,cyberroadie/go,fjballest/golang,cloudflare/go,goodlang/good,miolini/go,roth1002/go,akutz/go,codestation/go,suncycheng/go,akutz/go,theif519/go,roth1002/go,akutz/go,deft-code/go,binarycrusader/go,goodlang/good,codestation/go,cloudflare/go,Cofyc/go,fjballest/golang,vanloswang/go,goodlang/good,roth1002/go,4ad/go,Cofyc/go,josharian/go,miolini/go,cloudflare/go,sndnvaps/go,ImJasonH/go,odeke-em/go,golang/go,binarycrusader/go,cyberroadie/go,momchil-velikov/go,CAFxX/go,nawawi/go,goodlang/good,miolini/go,mwhudson/go,Samurais/go,suncycheng/go,cyberroadie/go,cyberroadie/go,Endika/go,ImJasonH/go,ImJasonH/go,CAFxX/go,cyberroadie/go,kim-racktop/go,akutz/go,codestation/go,deft-code/go,golang/go,codestation/go,Endika/go,Samurais/go,sndnvaps/go,polyverse-security/go,sndnvaps/go,deft-code/go,goodlang/good,sndnvaps/go,vsekhar/elastic-go,ImJasonH/go,goodlang/good,binarycrusader/go,Endika/go,fjballest/golang,nawawi/go,odeke-em/go,theif519/go,ganboing/go-esx,suncycheng/go,fjballest/golang,Endika/go,odeke-em/go,linux-on-ibm-z/go,nawawi/go,kim-racktop/go,linux-on-ibm-z/go,linux-on-ibm-z/go,codestation/go,binarycrusader/go,nawawi/go,vsekhar/elastic-go,fjballest/golang,theif519/go,derekmarcotte/go,binarycrusader/go,miolini/go,deft-code/go,josharian/go,golang/go,CAFxX/go,deft-code/go,derekmarcotte/go,sndnvaps/go,goodlang/good