Enable overriding build flags from environment

README.md

@@ -157,6 +157,7 @@ Because the subcommands and flags are constrained to benefit rapid plugin protot
 - `XCADDY_SKIP_BUILD=1` causes xcaddy to not compile the program, it is used in conjunction with build tools such as [GoReleaser](https://goreleaser.com). Implies `XCADDY_SKIP_CLEANUP=1`.
 - `XCADDY_SKIP_CLEANUP=1` causes xcaddy to leave build artifacts on disk after exiting.
 - `XCADDY_WHICH_GO` sets the go command to use when for example more then 1 version of go is installed.
+- `XCADDY_GO_BUILD_FLAGS` overrides default build arguments. Supports Unix-style shell quoting, for example: XCADDY_GO_BUILD_FLAGS="-ldflags '-w s'".
 ---
 
 © 2020 Matthew Holt

builder.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/Masterminds/semver/v3"
 	"github.com/caddyserver/xcaddy/internal/utils"
+	"github.com/google/shlex"
 )
 
 // Builder can produce a custom Caddy build with the
@@ -45,6 +46,7 @@ type Builder struct {
 	SkipCleanup  bool          `json:"skip_cleanup,omitempty"`
 	SkipBuild    bool          `json:"skip_build,omitempty"`
 	Debug        bool          `json:"debug,omitempty"`
+	BuildFlags   string        `json:"build_flags,omitempty"`
 }
 
 // Build builds Caddy at the configured version with the
@@ -115,10 +117,19 @@ func (b Builder) Build(ctx context.Context, outputFile string) error {
 		// support dlv
 		cmd.Args = append(cmd.Args, "-gcflags", "all=-N -l")
 	} else {
-		cmd.Args = append(cmd.Args,
-			"-ldflags", "-w -s", // trim debug symbols
-			"-trimpath",
-		)
+		if b.BuildFlags != "" {
+			// override build flags from environment if given
+			flags, err := shlex.Split(b.BuildFlags)
+			if err != nil {
+				log.Fatalf("[FATAL] Splitting arguments failed: %s", b.BuildFlags)
+			}
+			cmd.Args = append(cmd.Args, flags...)
+		} else {
+			cmd.Args = append(cmd.Args,
+				"-ldflags", "-w -s", // trim debug symbols
+				"-trimpath",
+			)
+		}
 	}
 
 	if b.RaceDetector {

cmd/main.go

@@ -40,6 +40,7 @@ var (
 	skipBuild        = os.Getenv("XCADDY_SKIP_BUILD") == "1"
 	skipCleanup      = os.Getenv("XCADDY_SKIP_CLEANUP") == "1" || skipBuild
 	buildDebugOutput = os.Getenv("XCADDY_DEBUG") == "1"
+	buildFlags       = os.Getenv("XCADDY_GO_BUILD_FLAGS")
 )
 
 func Main() {
@@ -134,6 +135,7 @@ func runBuild(ctx context.Context, args []string) error {
 		SkipBuild:    skipBuild,
 		SkipCleanup:  skipCleanup,
 		Debug:        buildDebugOutput,
+		BuildFlags:   buildFlags,
 	}
 	err := builder.Build(ctx, output)
 	if err != nil {

environment.go

@@ -98,6 +98,7 @@ func (b Builder) newEnvironment(ctx context.Context) (*environment, error) {
 		tempFolder:      tempFolder,
 		timeoutGoGet:    b.TimeoutGet,
 		skipCleanup:     b.SkipCleanup,
+		buildFlags:      b.BuildFlags,
 	}
 
 	// initialize the go module
@@ -177,6 +178,7 @@ type environment struct {
 	tempFolder      string
 	timeoutGoGet    time.Duration
 	skipCleanup     bool
+	buildFlags      string
 }
 
 // Close cleans up the build environment, including deleting

go.mod

@@ -2,4 +2,7 @@ module github.com/caddyserver/xcaddy
 
 go 1.14
 
-require github.com/Masterminds/semver/v3 v3.1.1
+require (
+	github.com/Masterminds/semver/v3 v3.1.1
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
+)

go.sum

@@ -1,2 +1,4 @@
 github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc=
 github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=