Enable parallel compilation by splitting targets per architecture

[okankoAMZ]

Problem

The Makefile builds all architectures sequentially within each platform target. On a multi-core machine, make amazon-cloudwatch-agent-linux took ~75s because amd64 and arm64 binaries were compiled one after the other.

Changes

Split build targets by architecture and enable automatic parallel builds:

• Add MAKEFLAGS += -j4 for automatic parallelization (4 parallel jobs)
• Split amazon-cloudwatch-agent-linux into amazon-cloudwatch-agent-linux-amd64 + amazon-cloudwatch-agent-linux-arm64 sub-targets
• Split amazon-cloudwatch-agent-darwin into amazon-cloudwatch-agent-darwin-amd64 + amazon-cloudwatch-agent-darwin-arm64 sub-targets
• Add explicit build dependencies to package-prepare-* targets to prevent race conditions

Before

graph TD
 build["make build"]

 build --> linux
 build --> darwin
 build --> windows

 subgraph Linux["⛓️ Linux (sequential — bottleneck)"]
 linux["amazon-cloudwatch-agent-linux"]
 copy_ver1["copy-version-file"]
 workload_linux["workload-discovery-linux"]
 amd64_seq["🔴 Build AMD64<br/>(runs first)"]
 arm64_seq["🔴 Build ARM64<br/>(blocked — waits for AMD64)"]
 linux --> copy_ver1
 linux --> workload_linux
 linux ==> amd64_seq
 amd64_seq ==>|"must finish before"| arm64_seq
 end

 subgraph Darwin["⛓️ Darwin (sequential — bottleneck)"]
 darwin["amazon-cloudwatch-agent-darwin"]
 copy_ver2["copy-version-file"]
 workload_darwin["workload-discovery-darwin"]
 amd64_seq2["🔴 Build AMD64<br/>(runs first)"]
 arm64_seq2["🔴 Build ARM64<br/>(blocked — waits for AMD64)"]
 darwin --> copy_ver2
 darwin --> workload_darwin
 darwin ==> amd64_seq2
 amd64_seq2 ==>|"must finish before"| arm64_seq2
 end

 subgraph Windows
 windows["amazon-cloudwatch-agent-windows"]
 end

 subgraph Packaging["Packaging (no explicit dependencies)"]
 package_rpm["package-prepare-rpm"]
 package_deb["package-prepare-deb"]
 package_win["package-prepare-win-zip"]
 package_darwin_tar["package-prepare-darwin-tar"]
 end

 package_rpm -.no explicit dependency.-> linux
 package_deb -.no explicit dependency.-> linux
 package_win -.no explicit dependency.-> windows
 package_darwin_tar -.no explicit dependency.-> darwin

 style amd64_seq stroke:#ff6b6b,stroke-width:3px
 style arm64_seq stroke:#ff6b6b,stroke-width:3px
 style amd64_seq2 stroke:#ff6b6b,stroke-width:3px
 style arm64_seq2 stroke:#ff6b6b,stroke-width:3px
 style linux stroke:#ffa500,stroke-width:2px
 style darwin stroke:#ffa500,stroke-width:2px

Loading

After

graph LR
 build["make build"]

 subgraph Linux["Linux (parallel)"]
 linux["amazon-cloudwatch-agent-linux"]
 linux_amd64["amazon-cloudwatch-agent-linux-amd64"]
 linux_arm64["amazon-cloudwatch-agent-linux-arm64"]
 copy_ver1["copy-version-file"]
 workload_linux["workload-discovery-linux"]
 linux --> linux_amd64
 linux --> linux_arm64
 linux_amd64 --> copy_ver1
 linux_amd64 --> workload_linux
 linux_arm64 --> copy_ver1
 linux_arm64 --> workload_linux
 end

 subgraph Darwin["Darwin (parallel)"]
 darwin["amazon-cloudwatch-agent-darwin"]
 darwin_amd64["amazon-cloudwatch-agent-darwin-amd64"]
 darwin_arm64["amazon-cloudwatch-agent-darwin-arm64"]
 copy_ver2["copy-version-file"]
 workload_darwin["workload-discovery-darwin"]
 darwin --> darwin_amd64
 darwin --> darwin_arm64
 darwin_amd64 --> copy_ver2
 darwin_amd64 --> workload_darwin
 darwin_arm64 --> copy_ver2
 darwin_arm64 --> workload_darwin
 end

 subgraph Windows
 windows["amazon-cloudwatch-agent-windows"]
 end

 build --> linux
 build --> darwin
 build --> windows

 subgraph Packaging["Packaging (explicit dependencies)"]
 package_rpm["package-prepare-rpm"]
 package_deb["package-prepare-deb"]
 package_win["package-prepare-win-zip"]
 package_darwin_tar["package-prepare-darwin-tar"]
 end

 package_rpm --> linux
 package_deb --> linux
 package_win --> windows
 package_darwin_tar --> darwin

 style linux_amd64 stroke:#51cf66
 style linux_arm64 stroke:#51cf66
 style darwin_amd64 stroke:#51cf66
 style darwin_arm64 stroke:#51cf66
 style linux stroke:#339af0
 style darwin stroke:#339af0
 style package_rpm stroke:#a78bfa
 style package_deb stroke:#a78bfa
 style package_win stroke:#a78bfa
 style package_darwin_tar stroke:#a78bfa

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Tests

Local benchmarks (32-core machine)

Target	Before	After	Speedup
amazon-cloudwatch-agent-linux	74.93s	6.22s	12x
make build (all platforms)	~90s	6.44s	~14x

CI benchmarks (non-cached, vs run #1679)

Job	Before	After	Speedup
BuildAndUpload / MakeBinary	13m 45s	3m 47s	3.6x
BuildAndUploadCN / MakeBinary	15m 9s	4m 9s	3.6x
BuildAndUploadITAR / MakeBinary	13m 55s	5m 23s	2.6x
MakeMacPkg	11m 27s	3m 38s	3.2x

Backwards compatibility

All existing top-level targets (make build, make release, make amazon-cloudwatch-agent-linux, etc.) are preserved — fully backwards compatible.