ci: retry/back off toolchain downloads

Earthfile

@@ -124,7 +124,9 @@ lint:
     RUN apk add --no-cache curl
     # renovate: datasource=github-releases packageName=golangci/golangci-lint
     LET golangci_lint_version=2.12.2
-    RUN curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/main/install.sh | sh -s -- -b $(go env GOPATH)/bin v$golangci_lint_version
+    RUN curl -sSfL --retry 7 --retry-all-errors -o /tmp/golangci-install.sh https://raw.githubusercontent.com/golangci/golangci-lint/main/install.sh && \
+        sh /tmp/golangci-install.sh -b $(go env GOPATH)/bin v$golangci_lint_version && \
+        rm /tmp/golangci-install.sh
     COPY ./.golangci.yaml .
     COPY --dir +code/earthly /
     FOR mod_path IN $(find . -name go.mod -print0 | xargs -0 dirname)

ast/parser/Earthfile

@@ -9,8 +9,7 @@ RUN apk add --no-cache ca-certificates curl openssl go && \
 WORKDIR /usr/local/lib
 # renovate: datasource=github-releases packageName=antlr/antlr4
 ARG --global ANTLR_VERSION=4.13.1
-RUN echo curl -O https://www.antlr.org/download/antlr-${ANTLR_VERSION}-complete.jar
-RUN curl -O https://www.antlr.org/download/antlr-${ANTLR_VERSION}-complete.jar
+RUN curl -fSLO --retry 7 --retry-all-errors https://www.antlr.org/download/antlr-${ANTLR_VERSION}-complete.jar
 WORKDIR /earthly
 
 parser:

examples/zig/Earthfile

@@ -13,13 +13,21 @@ deps:
         ARG ZIG_ARCH="aarch64"
     END
     RUN echo "Installing Zig $ZIG_VERSION for $ZIG_ARCH"
+    # ziglang.org throttles/drops CI downloads; on top of wget's own rapid
+    # retries, back off between attempts — rapid retries hit the same
+    # throttle and all fail.
     RUN \
         if echo "$ZIG_VERSION" | grep -q -- "-dev"; then \
             export URL="https://ziglang.org/builds/zig-$ZIG_ARCH-linux-$ZIG_VERSION.tar.xz"; \
         else \
             export URL="https://ziglang.org/download/$ZIG_VERSION/zig-$ZIG_ARCH-linux-$ZIG_VERSION.tar.xz"; \
         fi && \
-        wget --tries=5 --timeout=300 --continue -O zig.tar.xz "$URL" && \
+        for i in 1 2 3 4 5; do \
+            wget -t 5 -T 300 -c -O zig.tar.xz "$URL" && break; \
+            [ "$i" -lt 5 ] || exit 1; \
+            echo "Zig download attempt $i/5 failed; retrying" >&2; \
+            sleep $((i * 10)); \
+        done && \
         mkdir zig && \
         tar -xvf zig.tar.xz --strip-components 1 -C zig && \
         ln -sf /zig/zig /usr/bin/zig

tests/cloud-push-pull/Earthfile

@@ -10,7 +10,7 @@ all:
     BUILD +amazon-elastic-container-registry
 
 google-base:
-    RUN curl -O https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-sdk-420.0.0-linux-x86_64.tar.gz && \
+    RUN curl -fO --retry 7 --retry-all-errors https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-sdk-420.0.0-linux-x86_64.tar.gz && \
         tar -xvzf google-cloud-sdk-420.0.0-linux-x86_64.tar.gz && \
         ./google-cloud-sdk/install.sh -q && \
         ls -la /test/google-cloud-sdk

tests/with-docker-kind/Earthfile

@@ -14,7 +14,11 @@ all:
 alpine-kind:
     ARG DIND_IMAGE=earthbuild/dind:alpine-3.22-docker-28.3.3-r5
     FROM $DIND_IMAGE
-    RUN wget -O ./kind https://kind.sigs.k8s.io/dl/v$KIND_VERSION/kind-linux-amd64 && chmod +x kind
+    RUN for i in 1 2 3 4 5; do \
+            wget -c -T 60 -O ./kind https://kind.sigs.k8s.io/dl/v$KIND_VERSION/kind-linux-amd64 && break; \
+            [ "$i" -lt 5 ] || exit 1; \
+            sleep $((i * 5)); \
+        done && chmod +x kind
     WITH DOCKER
         RUN (update-alternatives --set iptables /usr/sbin/iptables-legacy || true) && ./kind create cluster --verbosity 99999 --retain || { \
                 ./kind export logs ./logs && \
@@ -26,7 +30,7 @@ alpine-kind:
 ubuntu-kind:
     ARG DIND_IMAGE=earthbuild/dind:ubuntu-24.04-docker-28.4.0-1
     FROM $DIND_IMAGE
-    RUN curl -Lo ./kind https://kind.sigs.k8s.io/dl/v$KIND_VERSION/kind-linux-amd64 && chmod +x kind
+    RUN curl -fLo ./kind --retry 7 --retry-all-errors https://kind.sigs.k8s.io/dl/v$KIND_VERSION/kind-linux-amd64 && chmod +x kind
     WITH DOCKER
         RUN ./kind create cluster --verbosity 99999 --retain || { \
                 ./kind export logs ./logs && \