Here is a patch to make it work on raspberrypi (armv7h) :

diff --git a/PKGBUILD b/PKGBUILD
index eb75eea..8df42c2 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -4,16 +4,24 @@ pkgname=prometheus-push-gateway-bin
 pkgver=0.4.0
 pkgrel=1
 pkgdesc="Prometheus push acceptor for ephemeral and batch jobs "
-arch=('x86_64')
+arch=('x86_64' 'armv7h')
 url="https://github.com/prometheus/pushgateway"
 license=('Apache')
 makedepends=()
-source=("https://github.com/prometheus/pushgateway/releases/download/v${pkgver}/pushgateway-${pkgver}.linux-amd64.tar.gz"
+source_x86_64=("https://github.com/prometheus/pushgateway/releases/download/v${pkgver}/pushgateway-${pkgver}.linux-amd64.tar.gz"
         "prometheus-push-gateway.service")
-sha256sums=('e1ce58b3f2c44816e748278434d6fc91e530da77dcc34b1246e1a0f25314831f'
+source_armv7h=("https://github.com/prometheus/pushgateway/releases/download/v${pkgver}/pushgateway-${pkgver}.linux-armv7.tar.gz"
+        "prometheus-push-gateway.service")
+sha256sums_x86_64=('e1ce58b3f2c44816e748278434d6fc91e530da77dcc34b1246e1a0f25314831f'
             'fe0ec9b3f18f2f35177fdf8dd8bd5ef0cee3189b65051b4239ad2ba1f5e9961c')
+sha256sums_armv7h=('539c2e4d4258cc70bc54893b64abc9453d543eba5f942be9836751d842f1410c'
+                   'fe0ec9b3f18f2f35177fdf8dd8bd5ef0cee3189b65051b4239ad2ba1f5e9961c')

 package() {
-    install -Dm755 "${srcdir}/pushgateway-${pkgver}.linux-amd64/pushgateway" "${pkgdir}/usr/bin/prometheus-push-gateway"
+    case "$CARCH" in
+            'x86_64') ARCH='amd64';;
+            'armv7h') ARCH='armv7';;
+    esac
+    install -Dm755 "${srcdir}/pushgateway-${pkgver}.linux-${ARCH}/pushgateway" "${pkgdir}/usr/bin/prometheus-push-gateway"
     install -Dm755 "${srcdir}/prometheus-push-gateway.service" "${pkgdir}/usr/lib/systemd/system/prometheus-push-gateway.service"
 }