Add Linux ARM64 native support

[garyschulte]

fixes #57

Adds support for building linux arm64 libs :

• adds arn64 gravition executor to circle ci
• adds arm64 lib copy task for secp256k1 and r1, ipa-multipoint, altbn128
• uses c_lib platform-specific char type in altbn128 to avoid unsigned char problem on linux arm64 / libc6 2.28
• adds OSARCH prefixing of build artifacts to prevent lib name conflicts
• adds linux arm64 arch detection to skip bls12-381 build (due to unsigned char type mismatch in rust)

BLS12-381 is intentionally omitted from the linux-arm64 build because:

1. we want to switch to blst
2. it is unnecessary to merge unsigned char fix upstream
3. the precompile isn't currently part of any besu protocol schedule

since this is a change to the layout of the native jars, I tested besu with 0.5.0-SNAPSHOT libs on all three platform identifiers:
linux-gnu-x86_64

2022-05-23 15:05:21.111-07:00 | main | INFO  | Besu | Using LibEthPairings native alt bn128
2022-05-23 15:05:21.112-07:00 | main | INFO  | Besu | Using the native implementation of the signature algorithm
2022-05-23 15:05:21.115-07:00 | main | INFO  | Besu | Starting Besu version: besu/v22.4.2-dev-7ea97fd5/linux-x86_64/openjdk-java-11
...

darwin (m1)

2022-05-23 15:10:21.616-07:00 | main | INFO  | Besu | Using LibEthPairings native alt bn128
2022-05-23 15:10:21.617-07:00 | main | INFO  | Besu | Using the native implementation of the signature algorithm
2022-05-23 15:10:21.620-07:00 | main | INFO  | Besu | Starting Besu version: besu/v22.4.2-dev-7ea97fd5/osx-aarch_64/oracle-java-17
...

linux-gnu-aarch64

2022-05-23 15:54:47.362-07:00 | main | INFO  | Besu | Using LibEthPairings native alt bn128
2022-05-23 15:54:47.389-07:00 | main | INFO  | Besu | Using the native implementation of the signature algorithm
2022-05-23 15:54:47.419-07:00 | main | INFO  | Besu | Starting Besu version: besu/v22.4.2-dev-5cdda94a/linux-aarch_64/oracle-java-17
...

For contrast, besu running on arm64-linux currently gives this output at startup:

2022-05-23 22:17:43.912+00:00 | main | INFO  | SECP256K1 | Native secp256k1 not available
2022-05-23 22:17:43.915+00:00 | main | INFO  | Besu | Using the Java implementation of alt bn128
2022-05-23 22:17:43.915+00:00 | main | INFO  | Besu | Using the Java implementation of the signature algorithm
2022-05-23 22:17:43.918+00:00 | main | INFO  | Besu | Starting Besu version: besu/v22.4.1/linux-aarch_64/openjdk-java-11
...
2022-05-23 22:17:44.467+00:00 | main | INFO  | AbstractAltBnPrecompiledContract | Native alt bn128 not available
2022-05-23 22:17:44.468+00:00 | main | INFO  | AbstractAltBnPrecompiledContract | Native alt bn128 not available
2022-05-23 22:17:44.469+00:00 | main | INFO  | AbstractAltBnPrecompiledContract | Native alt bn128 not available

[jclapis]

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