RTS: Reduce MBLOCK_SPACE_SIZE on AArch64
RTS: Reduce MBLOCK_SPACE_SIZE on AArch64

Commit 0d1a8d09f4 added a two step allocator for 64 bit systems. This
allocator mmaps a huge (1 TB) chunk of memory out of which it does
smaller allocations. On AArch64/Arm64 linux, this mmap was failing
due to the Arm64 Linux kernel parameter CONFIG_ARM64_VA_BITS
defaulting to 39 bits.

Therefore reducing the AArch64 value for MBLOCK_SPACE_SIZE to make
this allocation 1/4 TB while remaining 1 TB for other archs.

Reviewers: ezyang, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1171

GHC Trac Issues: #10682

oldmanmike/ghc,mfine/ghc,vTurbine/ghc,ghc-android/ghc,oldmanmike/ghc,shlevy/ghc,snoyberg/ghc,sgillespie/ghc,ghc-android/ghc,shlevy/ghc,shlevy/ghc,tjakway/ghcjvm,olsner/ghc,nushio3/ghc,oldmanmike/ghc,tjakway/ghcjvm,sdiehl/ghc,olsner/ghc,AlexanderPankiv/ghc,gridaphobe/ghc,ghc-android/ghc,ml9951/ghc,acowley/ghc,shlevy/ghc,ezyang/ghc,nushio3/ghc,wxwxwwxxx/ghc,GaloisInc/halvm-ghc,da-x/ghc,oldmanmike/ghc,mettekou/ghc,ghc-android/ghc,snoyberg/ghc,oldmanmike/ghc,sdiehl/ghc,acowley/ghc,sdiehl/ghc,vTurbine/ghc,olsner/ghc,nushio3/ghc,GaloisInc/halvm-ghc,vTurbine/ghc,elieux/ghc,snoyberg/ghc,siddhanathan/ghc,wxwxwwxxx/ghc,mcschroeder/ghc,nushio3/ghc,sdiehl/ghc,GaloisInc/halvm-ghc,elieux/ghc,gridaphobe/ghc,oldmanmike/ghc,ezyang/ghc,gridaphobe/ghc,mfine/ghc,tjakway/ghcjvm,GaloisInc/halvm-ghc,vTurbine/ghc,gridaphobe/ghc,sgillespie/ghc,nushio3/ghc,sgillespie/ghc,tjakway/ghcjvm,gridaphobe/ghc,AlexanderPankiv/ghc,ezyang/ghc,ezyang/ghc,mcschroeder/ghc,mcschroeder/ghc,mettekou/ghc,AlexanderPankiv/ghc,ml9951/ghc,ghc-android/ghc,anton-dessiatov/ghc,vikraman/ghc,sdiehl/ghc,AlexanderPankiv/ghc,siddhanathan/ghc,nkaretnikov/ghc,da-x/ghc,vikraman/ghc,olsner/ghc,vikraman/ghc,sgillespie/ghc,gridaphobe/ghc,da-x/ghc,wxwxwwxxx/ghc,da-x/ghc,sgillespie/ghc,mfine/ghc,vikraman/ghc,olsner/ghc,ml9951/ghc,shlevy/ghc,olsner/ghc,acowley/ghc,anton-dessiatov/ghc,sdiehl/ghc,siddhanathan/ghc,olsner/ghc,mcschroeder/ghc,anton-dessiatov/ghc,elieux/ghc,nkaretnikov/ghc,nkaretnikov/ghc,snoyberg/ghc,wxwxwwxxx/ghc,acowley/ghc,mettekou/ghc,snoyberg/ghc,elieux/ghc,sdiehl/ghc,shlevy/ghc,tjakway/ghcjvm,siddhanathan/ghc,acowley/ghc,sgillespie/ghc,nkaretnikov/ghc,mcschroeder/ghc,ml9951/ghc,tjakway/ghcjvm,da-x/ghc,ml9951/ghc,ghc-android/ghc,vikraman/ghc,mfine/ghc,anton-dessiatov/ghc,ml9951/ghc,sgillespie/ghc,anton-dessiatov/ghc,acowley/ghc,mfine/ghc,wxwxwwxxx/ghc,GaloisInc/halvm-ghc,shlevy/ghc,oldmanmike/ghc,da-x/ghc,AlexanderPankiv/ghc,nushio3/ghc,ml9951/ghc,siddhanathan/ghc,snoyberg/ghc,mcschroeder/ghc,GaloisInc/halvm-ghc,da-x/ghc,ghc-android/ghc,nushio3/ghc,vTurbine/ghc,elieux/ghc,tjakway/ghcjvm,mettekou/ghc,nkaretnikov/ghc,nkaretnikov/ghc,siddhanathan/ghc,nkaretnikov/ghc,AlexanderPankiv/ghc,elieux/ghc,vTurbine/ghc,siddhanathan/ghc,anton-dessiatov/ghc,ezyang/ghc,mfine/ghc,ezyang/ghc,elieux/ghc,GaloisInc/halvm-ghc,vikraman/ghc,anton-dessiatov/ghc,wxwxwwxxx/ghc,acowley/ghc,mettekou/ghc,snoyberg/ghc,mettekou/ghc,AlexanderPankiv/ghc,mfine/ghc,gridaphobe/ghc,vikraman/ghc,mettekou/ghc,wxwxwwxxx/ghc,mcschroeder/ghc,vTurbine/ghc,ml9951/ghc,ezyang/ghc